Why do I have spider mites on my hydroponic plants?

Spider mites are arachnids, not insects, so most standard insecticides have little effect on them. First sign is usually pale or yellow speckling on the upper leaf surface. Treat with a rotating miticide, spray during lights-off, and remove the worst-affected leaves. Prevent by keeping humidity above 60% RH and temperatures below 25°C.

How do I get rid of fungus gnats in hydroponics?

Adult gnats are mostly a nuisance; the larvae living in the growing media do the actual damage. Let the top layer of media dry between waterings to break the larval lifecycle, and combine sticky traps for adults with a larval treatment applied to the media at the same time.

How do I control scale insects on hydroponic plants?

Scale appear as small raised bumps or a waxy coating on stems and leaves. Horticultural oil or insecticidal soap works by suffocating them on contact. Repeat treatment every 7 to 10 days and prune away heavily infested stems rather than treating them in place.

How do I treat powdery mildew in my grow room?

Powdery mildew spores are present in ambient air almost everywhere, so the goal is preventing the conditions it needs rather than excluding exposure. Keep humidity below 50% during late flowering, treat at the very first sign of white powdery patches, and rotate fungicide products between applications.

How do I get rid of aphids on hydroponic plants?

Aphids are soft-bodied sap suckers that cluster on new growth and leaf undersides. Neem oil and pyrethrum-based sprays are the most effective botanical treatments available in Australia. Yellow sticky traps near the canopy catch winged aphids before a colony establishes.

How do I treat mealybugs in hydroponics?

Mealybugs show up as white waxy powder with cottony egg masses, usually in leaf joints and along stems. Apply 70% isopropyl alcohol directly to individual insects with a cotton swab to dissolve their protective wax coating on contact.

How do I get rid of thrips in hydroponics?

Thrips damage shows as silvery streaking and distorted new growth. Treat during the lights-off period, target the underside of leaves where thrips shelter, and use blue sticky traps, which catch thrips more effectively than yellow.

How do I stop root rot in hydroponics?

Root rot is almost always caused by Pythium, a water mould, so antifungal products don't treat it effectively. Healthy roots are white or cream and firm; infected roots turn brown or grey with a slimy coating and a fishy smell. Reservoir temperature above 22°C reduces dissolved oxygen and above 26°C Pythium can establish within 24 to 48 hours. Act immediately by dropping reservoir temperature, boosting aeration, trimming affected roots, and treating with hydrogen peroxide at roughly 3ml per litre.

How do I treat grey mould (botrytis) on my flowers?

Botrytis needs both high humidity and dead or dying plant matter to establish. Genetics play a major role, with some strains and phenotypes naturally resistant and others highly susceptible regardless of environment. Keep humidity around 55% RH during late flowering as a realistic practical minimum, keep air actively circulating with an oscillating fan or other climate control equipment, and remove dead leaves and spent flowers promptly, especially near or on bud sites. If botrytis keeps recurring despite good airflow and hygiene, researching your specific genetics is the best starting point.

What EC should I run for my hydroponic crop?

Target EC depends on crop type and growth stage, generally lower during seedling or clone stage and higher through vegetative and flowering. Evaporation concentrates the nutrient solution faster than plants take it up, so EC creeping upward over several days is expected. Top up a rising reservoir with plain water rather than more nutrient solution.

Why do my plants show deficiency symptoms even though I'm feeding correctly? (Nutrient lockout)

If plants show deficiency symptoms despite a correctly mixed feed, check pH first. Most lockout is a pH problem blocking uptake rather than an actual nutrient shortage. Salt buildup in the growing media over time can also block nutrient uptake even when the reservoir solution is correct. A full flush with plain, pH-adjusted water clears salt buildup.

How much Cal-Mag do I need in hydroponics?

Calcium and magnesium deficiency shows as interveinal chlorosis, yellowing between the leaf veins, and is most common on RO or naturally soft water. High-intensity LED lighting increases calcium and magnesium demand, making deficiency more likely even on otherwise adequate feed. A dedicated Cal-Mag supplement corrects this faster than adjusting base nutrient ratios.

What's the difference between nutrient burn and transplant shock?

Nutrient burn shows as crispy, browning leaf tips and edges, typically starting on the oldest, lowest leaves. Transplant shock shows as general wilting and slowed growth shortly after moving or disturbing a plant, without the crisped leaf-edge pattern. Nutrient burn needs a flush and reduced feed strength; transplant shock needs time and stable conditions, not less feed.

Why is my hydroponic water pump not working properly?

A humming pump that isn't moving water usually indicates an airlock or a jammed impeller, not a failed motor. Mineral crystallisation from hard water can build up on the impeller over time. A pump left running dry, even briefly, can damage the seal and cause ongoing weak flow afterward.

Why is my DWC bucket losing oxygen or smelling bad?

A bad smell and declining plant health in a DWC bucket usually means dissolved oxygen has dropped low enough for anaerobic bacteria to take hold. Check the air stone for clogging first, since a partially blocked stone reduces oxygen output before it fails completely. Increasing air pump output and dropping reservoir temperature both raise dissolved oxygen directly.

Why is my hydroponic reservoir turning green?

Green water almost always means algae, and algae needs light reaching the nutrient solution to establish. Common light leaks include lid edges that don't seal flush, net pot gaps, clear tubing and sight tubes. Full light exclusion using opaque reservoirs and tubing is the actual fix, since cleaning algae without sealing the leak means it comes back within days.

Should I use hydrogen peroxide or beneficial bacteria in my reservoir?

A sterile approach uses oxidisers like hydrogen peroxide to suppress microbial activity broadly. A bioactive approach introduces beneficial bacteria and fungi to the root zone instead. Oxidisers aren't selective and will undermine beneficial bacteria if used together, so pick one strategy per grow cycle rather than mixing both.

How do I clean biofilm from my hydroponic lines?

Biofilm is attached microbial and organic material inside wet tubing, drippers and fittings. Signs include uneven flow, gradually declining flow, and a slippery internal residue. Isolate the affected section, start with plain water and physical cleaning, and never let strong chemicals reach the reservoir or root zone while plants are connected.

Why are my indoor tomatoes and peppers not producing fruit?

No flowers at all usually points to plant maturity, insufficient light, temperature stress or excess nitrogen. Flowers that form but then drop point toward environmental stress, root-zone stress or a pollination problem, since even self-fertile flowers can fail to set fruit indoors without enough air movement.

Apex Grow Hydroponics

Hydroponic Troubleshooting Guide for Australian Growers

Not sure which of these you're looking at? Several problems on this page look almost identical on the plant. Nutrient burn and transplant shock, lockout and a genuine deficiency, spider mite stippling and early powdery mildew. PlantMDx asks for your pH, EC and what you can see, then narrows it to the likely cause and points you at the right section below. It's free, there's no signup, and it takes about a minute.

Answers to the most common hydroponic problems, organised by category. Each entry gives you the direct fix. Click through to the full guide for step-by-step detail.

Not Sure What's Causing It? Search by Symptom

1. Pests and Diseases

What You're Seeing	Likely Cause	Jump To
Yellow speckling on leaf tops, fine webbing underneath	Spider mites	1.1
Tiny moving dots on leaves, plant looks dusty or bronzed	Spider mites	1.1
Gnats keep coming back even after treating with diatomaceous earth	Diatomaceous earth losing effect when wet	1.2
Tiny black flies around the base of plants or in the media	Fungus gnats	1.3
Larvae in the growing media, adult flies when disturbed	Fungus gnats	1.3
Small raised bumps or waxy coating on stems	Scale insects	1.4
White powdery coating spreading across leaves	Powdery mildew	1.5
Grey or white dust-like film that wipes off leaves	Powdery mildew	1.5
Sticky residue and clustered insects on new growth	Aphids	1.6
Curled new growth with tiny green or black bugs underneath	Aphids	1.6
White cottony clusters at leaf joints	Mealybugs	1.7
Silvery streaks on leaves, distorted new growth	Thrips	1.8
Black speckled droppings on leaf surfaces	Thrips	1.8
Brown, slimy, foul-smelling roots	Root rot	1.9
Roots gone brown instead of white, plant wilting	Root rot	1.9
Grey fuzzy mould on flowers or buds	Botrytis (grey mould)	1.10
Bud rot spreading from the inside of dense flowers	Botrytis (grey mould)	1.10
Seedling collapses right at the soil line	Damping off	1.11
Seedling stem goes thin and dark at the base then falls over	Damping off	1.11

2. pH, EC and Water

What You're Seeing	Likely Cause	Jump To
pH keeps dropping no matter how much I correct it	pH dropping	2.1
Adding pH up constantly and it doesn't hold	pH dropping	2.1
Not sure if my tap water is safe to use	Australian tap water suitability	2.2
Wondering if I need RO water for hydroponics	Australian tap water suitability	2.2
pH meter giving different readings every time	pH meter calibration	2.3
pH pen reading seems obviously wrong	pH meter calibration	2.3
Not sure what EC I should even be running	EC target by crop/stage	2.4
What EC should I run for my crop and stage	EC target by crop/stage	2.4
pH creeping up every day	pH rising	2.5
Adding pH down constantly and it climbs straight back	pH rising	2.5
EC drifting up or down and I don't know why	EC rising or falling	2.6
Reservoir getting stronger or weaker over a few days	EC rising or falling	2.6

3. Nutrients

What You're Seeing	Likely Cause	Jump To
Deficiency symptoms despite feeding correctly	Nutrient lockout	3.1
Feeding the right amount but plant still shows deficiency	Nutrient lockout	3.1
Yellowing between leaf veins, veins stay green	Cal-Mag deficiency	3.2
Brown spotting on new leaves, weak stems	Cal-Mag deficiency	3.2
Burnt leaf tips or edges	Nutrient burn	3.3
Leaves clawing downward with dark green colour	Nutrient burn	3.3

4. Pumps and Aeration

What You're Seeing	Likely Cause	Jump To
Water pump running but no water moving	Water pump failure	4.1
Pump humming but nothing coming out	Water pump failure	4.1
DWC bucket smells bad or oxygen seems low	DWC oxygen issues	4.2
Roots look slimy in a DWC bucket	DWC oxygen issues	4.2
Air stone gone quiet or barely bubbling	Blocked air stone	4.3
Bubbles used to be strong, now barely there	Blocked air stone	4.3

5. Environment and Reservoir

What You're Seeing	Likely Cause	Jump To
Reservoir water turning green	Algae / light leak	5.1
Green slime building up inside the tank	Algae / light leak	5.1
Not sure if I should run sterile or bioactive	Sterile vs bioactive reservoir	5.2
Slimy buildup inside tubing or fittings	Biofilm	5.3
Drippers clogging or flow slowing over time	Biofilm	5.3
Reservoir feels warm to the touch	Reservoir too hot	5.4
Water temperature climbing above 24C	Reservoir too hot	5.4

6. Plant Growth and Yield

What You're Seeing	Likely Cause	Jump To
Plant flowering but not producing fruit	Poor fruiting	6.1
Flowers dropping before fruit sets	Poor fruiting	6.1
Seedlings growing tall and thin, falling over	Seedling stretching	6.2
Big gaps between leaf sets on young plants	Seedling stretching	6.2
Leaves curling downward or clawing	Leaves curling	6.3
Leaves curling upward like a taco	Leaves curling	6.3
Plant wilting even though media is wet	Low root zone oxygen	6.4
Drooping despite reservoir being full and on schedule	Low root zone oxygen	6.4

If you already know the cause, jump straight to the category index below instead.

Already Know the Cause? Browse by Category

1. Pests and Diseases

1.1 Spider Mites
1.2 Diatomaceous Earth for Gnats
1.3 Fungus Gnats
1.4 Scale Insects
1.5 Powdery Mildew
1.6 Aphids
1.7 Mealybugs
1.8 Thrips
1.9 Root Rot
1.10 Grey Mould (Botrytis)
1.11 Damping Off

2. pH, EC and Water

2.1 pH Keeps Dropping
2.2 Australian Tap Water
2.3 pH Meter Inconsistent
2.4 What EC Should I Run
2.5 pH Keeps Rising
2.6 EC Rising or Falling

3. Nutrients

3.1 Nutrient Lockout
3.2 Cal-Mag Deficiency
3.3 Nutrient Burn vs Transplant Shock

4. Pumps and Aeration

4.1 Water Pump Not Working
4.2 DWC Losing Oxygen
4.3 Air Stone Not Bubbling

5. Environment and Reservoir Issues

5.1 Algae and Light Leaks
5.2 Sterile vs Bioactive Reservoir
5.3 Biofilm in Lines
5.4 Reservoir Too Hot

6. Plant Growth and Yield

6.1 Poor Fruit Production
6.2 Seedling Stretching
6.3 Leaves Curling or Clawing
6.4 Wilting Despite Water

1. Pests and Diseases

1.1 Quick Answer: Spider Mites in Hydroponics

Red spider mite infestation with fine webbing on a hydroponic plant leaf

Spider mites are arachnids, not insects, so most standard insecticides have little effect on them.
First sign is usually pale or yellow speckling on the upper leaf surface; check the underside of leaves for the mites themselves and fine webbing.
Treat with a miticide like Mite-Rid, rotating products between applications so mites don't build resistance.
Spray during the lights-off period and remove the worst-affected leaves before treating.
Prevent by keeping humidity above 60% RH and temperatures below 25C, conditions mites don't thrive in.

Full guide: Spider Mites in Australian Grow Rooms - Shop pest control products

1.2 Quick Answer: Does Diatomaceous Earth Kill Fungus Gnats?

Diatomaceous earth only works while completely dry, and loses its effect the moment growing media gets wet.
In an actively watered hydroponic system, media is wet most of the time, which is why DE alone often under-performs.
A moisture-resistant product like Gnat Nix holds up far better as a top dressing in wet conditions.
Letting the top layer of media dry out between waterings also interrupts the gnat larval lifecycle directly.

Full guide: Diatomaceous Earth for Fungus Gnats - Shop Gnat Nix

1.3 Quick Answer: How to Get Rid of Fungus Gnats

Fungus gnat larvae in wet growing media with an adult fungus gnat inset, showing both life stages

Adult gnats are mostly a nuisance; it's the larvae living in the growing media that actually damage roots.
Let the top layer of media dry between waterings to break the larval lifecycle.
Combine sticky traps for adults with a larval treatment like Gnat Nix applied to the media at the same time.
Treating only the adults without addressing larvae in the media means the problem returns within days.

Full guide: Fungus Gnats in Hydroponics - Shop Gnat Nix

1.4 Quick Answer: Scale Insects on Hydroponic Plants

Scale insect infestation on a plant stem showing waxy coating and young crawlers

Scale appear as small raised bumps or a waxy coating on stems and leaves, easy to mistake for a plant feature early on.
A horticultural oil or insecticidal soap works by suffocating them on contact; thorough coverage matters more than concentration.
Repeat treatment every 7 to 10 days, since a single application rarely gets every insect and egg.
Prune away heavily infested stems rather than trying to treat them in place.

Full guide: Scale Insects on Plants - Shop pest control products

1.5 Quick Answer: Powdery Mildew in the Grow Room

Powdery mildew white coating on a plant leaf

Powdery mildew spores are present in ambient air almost everywhere, so the goal is preventing the conditions it needs, not excluding exposure entirely.
Keep humidity below 50% during late flowering, when plants are most vulnerable.
Treat at the very first sign of white powdery patches with a product like Micro Kill rather than waiting for it to spread.
Rotate treatment products between applications to avoid resistance building up.

Full guide: Powdery Mildew Prevention and Treatment - Shop Micro Kill

1.6 Quick Answer: Aphids on Hydroponic Plants

Cotton aphid colony feeding on a leaf, showing multiple life stages

Aphids are soft-bodied sap suckers that cluster on new growth and the underside of leaves.
A botanical spray like Zero Tolerance is one of the most effective natural treatments readily available in Australia.
Yellow sticky traps placed near the canopy catch winged aphids before a colony has a chance to establish.

Full guide: Aphids on Hydroponic Plants - Shop Zero Tolerance

1.7 Quick Answer: Mealybugs in Hydroponics

Close-up of a mealybug showing its white cottony wax coating on a hydroponic plant

Mealybugs show up as white waxy powder with cottony egg masses, usually in leaf joints and along stems.
Isopropyl alcohol, diluted with water, applied directly to individual insects with a cotton swab dissolves their protective wax coating on contact.
Check leaf joints and stem crevices carefully, since mealybugs hide in gaps that sprays alone can miss.

Full guide: Mealybugs on Hydroponic Plants - Shop isopropyl alcohol

1.8 Quick Answer: Thrips in Hydroponics

Close-up of an adult thrips insect on a leaf surface

Thrips damage shows as silvery streaking and distorted new growth, often before you spot the insects themselves.
Treat during the lights-off period and target the underside of leaves where thrips shelter.
Blue sticky traps catch thrips more effectively than yellow, since thrips are more attracted to blue.

Full guide: Thrips on Hydroponic Plants - Shop pest control products

1.9 Quick Answer: Root Rot in Hydroponics

Almost always caused by Pythium, a water mould rather than a true fungus, so antifungal products don't treat it effectively.
Healthy roots are white or cream and firm; infected roots turn brown or grey with a slimy coating and a fishy or sewage-like smell.
Reservoir temperature is the biggest risk factor: above 22C dissolved oxygen drops, and above 26C Pythium can take hold within 24 to 48 hours.
Act immediately: drop reservoir temperature, boost aeration with air stones, trim away affected root tissue, and treat with Guardian Hydro Clean.
Prevent recurrence with full system sterilisation using Guardian Hydro Clean between grows.

Full guide: Root Rot in Hydroponics Australia - Shop aeration products

1.10 Quick Answer: Grey Mould (Botrytis) on Flowers

Grey mould (Botrytis) infection on flower buds and dried petals

Botrytis needs both high humidity and dead or dying plant matter to get established.
Genetics play a major role. Some strains and phenotypes are naturally resistant to botrytis, while others are highly susceptible almost regardless of environment.
Keep humidity around 55% RH during late flowering, when developing buds are most susceptible. This is a realistic practical minimum for most grow spaces rather than an extreme target.
Besides genetics, the two biggest factors are keeping air actively circulating through the grow space with an oscillating fan or other climate control equipment, and removing any dead or dying leaves promptly. This matters especially for leaves near or directly on bud sites, since these are the most common infection points.
If botrytis keeps recurring despite good airflow and hygiene, proper research into your specific genetics is the best starting point. Some genetic lines are simply far more prone to mould regardless of how well the environment is managed.

Full guide: Botrytis / Grey Mould in Flowering Plants - Shop Micro Kill - Shop climate control

1.11 Quick Answer: Damping Off in Hydroponic Seedlings

Damping off is a fungal problem that collapses seedlings right at the media line, a thin, water-soaked stem is the telltale sign.
It's driven almost entirely by excess surface moisture and poor airflow around young seedlings, not the nutrient program.
Once a seedling has collapsed at the stem, it cannot be saved, prevention matters far more than treatment here.
A gentle circulation fan across seedling trays reduces surface moisture and is one of the most effective single preventions.

Full guide: Damping Off in Hydroponic Seedlings - Shop clip fans - Shop Propagation Supplies

2. pH, EC and Water

2.1 Quick Answer: Why Does My pH Keep Dropping?

Falling pH is most often driven by nutrient uptake patterns and, later in a grow, by decaying root matter in the reservoir.
Check for early root health issues first, since a dropping pH can be an early warning sign of root problems before other symptoms appear.
Correct with a pH Up product, but treat the underlying cause rather than just chasing the number daily.

Full guide: Why Does My Hydroponic pH Keep Dropping? - Shop pH Up & Down

2.2 Quick Answer: Can I Use Australian Tap Water for Hydroponics?

Yes, you can use tap water for hydroponics in Australia, but its suitability varies significantly by city and region.
Hard water regions typically push pH upward and add background EC before you've dosed any nutrients at all.
Test your specific source water's pH and EC with a reliable EC meter before assuming a standard feeding schedule will apply as written.

Full guide: Australian Tap Water for Hydroponics - Shop pH & EC products

2.3 Quick Answer: Why Is My pH Meter Giving Inconsistent Readings?

Most inconsistent readings come from the probe, not the water. Recalibrate weekly using fresh pH buffer solution, not old or contaminated solution.
If readings still drift after a fresh calibration, the probe itself may be reaching end of life and need replacing.
Always store the probe wet using a proper probe care kit between uses; letting it dry out damages the sensing membrane permanently.

Full guide: Why Is My pH Meter Giving Inconsistent Readings? - Shop calibration kits

2.4 Quick Answer: What EC Should I Run?

Target EC depends on crop type and growth stage, generally lower during seedling/clone stage and higher through vegetative and flowering.
Evaporation concentrates the nutrient solution faster than plants take it up, so EC creeping upward over several days is expected, not a fault.
Top up a rising reservoir with plain water rather than more nutrient solution, checked with a digital EC meter.

Full guide: What EC Should I Run? - Shop EC meters

2.5 Quick Answer: Why Does My Hydroponic pH Keep Rising?

Rising pH is most often caused by alkaline source water, particularly in harder water areas like Adelaide or Perth.
Algae in the reservoir consumes CO2 during the day, which pushes pH upward as a side effect.
A small reservoir with less buffering capacity swings pH faster than a large one, in both directions.
Repeatedly dosing pH Down without addressing the underlying cause usually means it creeps back up again within a day.
Confirm your meter is reading accurately before assuming the water chemistry itself has changed.

Full guide: Why Does My Hydroponic pH Keep Rising? - Shop pH Up & Down

2.6 Quick Answer: Why Does My Hydroponic EC Keep Rising or Falling?

Rising EC almost always means water is evaporating or being taken up faster than nutrients, concentrating what's left in the reservoir.
Falling EC usually means plants are taking up nutrients faster than water, common during heavy vegetative growth.
A small daily drift is completely normal. React to the trend over several days, not to one single reading.
A sudden, large EC swing rather than a gradual drift points to a meter fault, a dosing mistake or a leak, not normal plant behaviour.

Full guide: Why Does My Hydroponic EC Keep Rising or Falling? - Shop EC meters

3. Nutrients

3.1 Quick Answer: Nutrient Lockout (Deficiency Despite Correct Feeding)

If plants show deficiency symptoms despite a correctly mixed feed, check pH first. Most lockout is a pH problem blocking uptake, not an actual nutrient shortage.
Salt buildup in the growing media over time can also block nutrient uptake even when the reservoir solution itself is correct.
A full flush with plain, pH-adjusted water clears salt buildup and gives you a clean baseline to re-diagnose from.

Full guide: Nutrient Lockout - Shop base nutrients

3.2 Quick Answer: Cal-Mag Deficiency

Calcium and magnesium deficiency shows as interveinal chlorosis (yellowing between leaf veins) and is most common on RO or naturally soft water.
High-intensity LED lighting increases a plant's calcium and magnesium demand, making deficiency more likely even on otherwise adequate feed.
A dedicated Cal-Mag supplement corrects this faster than adjusting base nutrient ratios alone.

Full guide: Cal-Mag Deficiency in Hydroponics - Shop Cal-Mag

3.3 Quick Answer: Nutrient Burn vs Transplant Shock

Nutrient burn shows as crispy, browning leaf tips and edges, typically starting on the oldest, lowest leaves first.
Transplant shock shows as general wilting and slowed growth shortly after moving or disturbing a plant, without the crisped leaf-edge pattern.
Telling them apart matters because the fixes are opposite: nutrient burn needs a flush and reduced feed strength, transplant shock needs time and stable conditions, not less feed.

Full guide: Nutrient Burn vs Transplant Shock - Shop base nutrients

4. Pumps and Aeration

4.1 Quick Answer: Why Is My Water Pump Not Working Properly?

A humming pump that isn't moving water usually indicates an airlock or a jammed impeller, not a failed motor.
Mineral crystallisation from hard water can build up on the impeller over time and restrict flow gradually rather than suddenly.
A pump left running dry, even briefly, can damage the seal. If it's beyond repair, a reliable replacement like the Rio HF submersible pump is a solid upgrade.

Full guide: Why Is My Water Pump Not Working Properly? - Shop water pumps

4.2 Quick Answer: DWC Bucket Losing Oxygen or Smelling Bad

A bad smell and declining plant health in a DWC bucket usually means dissolved oxygen has dropped low enough for anaerobic bacteria to take hold.
Check the air stone for clogging first, since a partially blocked stone reduces oxygen output well before it fails completely.
Increasing air pump output and dropping reservoir temperature both raise dissolved oxygen levels directly.

4.3 Quick Answer: Why Is My Air Stone Not Bubbling?

A blocked air stone is the most common cause, mineral scale and biofilm gradually clog the tiny pores that create bubbles.
Kinked or pinched airline tubing cuts off flow before it even reaches the stone.
A reversed or stuck check valve can block airflow entirely even though the pump itself is running fine.
Water depth matters, a pump underpowered for how deep the stone sits simply can't push air down against that pressure.

Full guide: Why Is My Air Stone Not Bubbling? - Shop air stones

5. Environment and Reservoir Issues

5.1 Quick Answer: Why Is My Reservoir Turning Green?

Green water almost always means algae, and algae needs light reaching the nutrient solution to establish, not just moisture and nutrients which are already present.
Common light leaks: lid edges that don't seal flush, net pot gaps, clear tubing, sight tubes, and light-coloured or clear reservoir walls.
Full light exclusion is the actual fix. Cleaning algae without sealing the light leak usually means it's back within days.
Use fully opaque reservoirs like the Tub 65L Black, opaque tubing, and a properly sealed lid to prevent it establishing in the first place.

Full guide: Algae and Light Leaks in Hydroponics - Shop opaque reservoirs

5.2 Quick Answer: Sterile or Bioactive Reservoir Management?

A sterile approach uses oxidisers like Guardian Hydro Clean to suppress microbial activity broadly. A bioactive approach introduces beneficial bacteria like Azos or fungi like Mykos to the root zone.
Oxidisers aren't selective. They don't distinguish between pathogens and the beneficial bacteria you're trying to establish.
Don't introduce beneficial bacteria while an active oxidiser is present. It will undermine the biological treatment before it has a chance to work.
Pick one primary strategy and only switch between cycles, with proper cleaning in between.

Full guide: Sterile vs Bioactive Reservoir Management - Shop Guardian Hydro Clean

5.3 Quick Answer: Cleaning Biofilm From Hydroponic Lines

Biofilm is attached microbial and organic material that builds up inside wet tubing, drippers and fittings, not something floating loose in the reservoir.
Signs of buildup include uneven flow between outlets, gradually declining flow, a slippery internal residue, and an off smell from tubing or fittings.
Isolate the affected plumbing section rather than running strong chemicals through lines still connected to living roots.
Start with plain water, disassembly and physical cleaning with a soft brush before considering anything stronger.

Full guide coming soon. - Shop fittings and drippers

5.4 Quick Answer: Why Is My Hydroponic Reservoir Too Hot?

Above 22C, dissolved oxygen starts dropping in the reservoir, and above 26C root pathogens like Pythium can establish within 24 to 48 hours.
The biggest heat sources are usually the grow light itself, ambient room temperature, and heat generated by the pump running inside the reservoir.
Moving the reservoir away from direct light, insulating or shading the tank, and increasing aeration all help without needing a dedicated chiller.
A dedicated water chiller is the most reliable fix if heat is a persistent, recurring problem rather than an occasional summer spike.

Full guide: Why Is My Hydroponic Reservoir Too Hot? - Shop opaque reservoirs

6. Plant Growth and Yield

6.1 Quick Answer: Why Are My Tomatoes and Peppers Not Fruiting?

No flowers at all usually points to plant maturity, insufficient light, temperature stress, or excess nitrogen delaying reproductive growth.
Flowers that form but then drop point toward environmental stress, root-zone stress, or a pollination problem rather than a nutrient issue.
Self-fertile flowers like tomatoes and most peppers can still fail to set fruit indoors without enough air movement to trigger pollen release.
Diagnose which stage is actually failing, no flowers, flower drop, or fruit that doesn't develop, before changing your nutrient program.

Full guide coming soon. - Shop Cal-Mag

6.2 Quick Answer: Why Are My Seedlings Stretching?

Stretching usually means light is too weak, too far away, or unevenly distributed across the tray, causing the seedling to grow upward searching for light.
Leggy seedlings show a long, thin stem with unusually large gaps between leaf sets, rather than compact growth.
The stem that has already stretched won't shorten back down, but correcting conditions improves all future growth from that point on.
A dedicated propagation fixture like the SANlight FLEX II is built for the correct seedling intensity range from the start.

Full guide: Seedling Stretching and Light Height - Shop propagation lighting

6.3 Quick Answer: Why Are My Leaves Curling or Clawing?

Leaves curling downward like claws most often points to nitrogen excess or overfeeding, especially with dark green, otherwise healthy-looking foliage.
Leaves curling upward can indicate heat stress or the light sitting too close to the canopy.
Curling combined with crispy or browning edges usually means nutrient burn from EC running too high.
Curling combined with wilting or drooping points toward a root problem rather than the leaves themselves.

Full guide: Why Are My Leaves Curling or Clawing? - Shop EC meters

6.4 Quick Answer: Why Is My Hydroponic Plant Wilting Even Though It Has Water?

Wilting despite adequate water almost always means roots can't actually take up that water, not that water is missing.
Low root zone oxygen is the most common cause, roots need oxygen to function, not just moisture.
Root rot, high EC and warm reservoir water are the three biggest reasons roots stop functioning properly.
An oversized pot in coco can cause the same problem from the opposite direction, too much wet media around a small root system stays saturated and low in oxygen, so it feels waterlogged rather than dry.

Full guide: Why Is My Hydroponic Plant Wilting Even Though It Has Water? - Shop O16 Stabilised Oxygen