Major Imbalance: High KH, Zero PO4, High Nitrate

[zoroi]

Tank Overview


Hi everyone,

I’m looking for some help and insight from the community to troubleshoot a few persistent issues in my reef tank. Here’s an overview of my setup:


System Details

• Age: 8 months running
• Display Tank: 80x40x40 cm (~128L)
• Sump: External ~40L
• Lighting: 2x Spectra Knight V3 + Maxspect Etherium (some LEDs might be burnt, but overall PAR coverage seems okay)
• Return Pump: Dymax 1800L/h
• Skimmer: NY 300 (Brazilian brand)
• Wave Maker: HSBAO 4000L/h with controller
• UV Filter: 32W Ocean Tech UV with 500L/h pump
• Temperature Control: Heater + fans managed by a temperature controller (kept between 25.5–26.5°C)
• ATO: Gravity-fed freshwater reservoir (with float valve)
• Other Filtration: Activated carbon and Purigen used occasionally
• Feeder: Automatic feeder using New Life Spectrum Ultra Red pellets

Livestock

Fish:

• 1 Clownfish
• 1 Firefish (currently in sump)
• 1 Midas Blenny
• 1 Aurora Goby
• 1 McCosker Flasher Wrasse
• 1 Yellow Coris Wrasse
• 1 Royal Gramma

Inverts:

• Assorted hermit crabs
• Assorted snails (including 1 Astraea)
• 1 BBT anemone
• 3 shrimp (Stenopus gold, Cleaner, Dancing shrimp)
• Several brittle stars
• 1 Urchin

Corals:

• Zoanthids
• Torch corals
• Trumpet coral
• Mushrooms
• Goniopora (some thriving, others declining)
• A few SPS
• See more at the pictures

Feeding & Dosing

• Fish food: Tropical and new life flakes/pellets once per day (increased quantity recently)
• Coral food: Pellet coral food twice per week
• Additives: Power Elixir twice per week
• Bacteria: Delta Fish live bacteria
• Phosphate: Dosing 0.2–0.4 ml/day of Colombo Phosphate+
• All-for-Reef: I stopped dosing over 2 months ago because my KH was staying high

Main Issues & Questions – Help Appreciated!

1. Persistently High KH (Above 9)
   • My KH has been hovering around 9–9.4 for the last 2–3 months.
   • I stopped dosing All-for-Reef over 2 months ago but the KH still won’t drop.
   • I’ve done significant water changes and still no decrease.
   • Any idea why KH won’t come down naturally?
2. Phosphate Reading Zero Despite Daily Dosing
   • I’m dosing Colombo phosphate daily but still reading zero phosphate.
   • My corals (especially torches and two gonioporas) show signs of stress — tissue slightly retracted.
   • Could this imbalance (high nitrate / zero phosphate) be a major stress factor?
3. Nitrate Levels High
   • Using Colombo test kit (max reading is 4ppm), I had to dilute the sample to get a reading around 12ppm — maybe even higher.
   • Is this imbalance (high NO3, zero PO4) affecting coral health, and what’s the best course of action to restore balance?

Other Context & Past Issues

• I’ve dealt with dinoflagellates before — now running UV 24/7 as part of prevention.
• I’m currently battling vermetid snails (sessile worms in tubular shells) — they irritate some corals.
• Hydroids also persist — I dose fenbendazole in long cycles.
• Recently, a lot of sponges have appeared — I suspect silicates are leaching from some component (possibly plastic/acrylic in the sump or tubing).
• Some corals seem happy (most mushrooms, some gonioporas), but others like torches are retracted, and two gonioporas are dying.

Any thoughts, experiences, or recommendations are very welcome — especially on managing the KH/PO4/NO3 balance, and ways to reduce silicates and vermetid snails. Thanks in advance!

Photos and tests:








(Zoas with sponges, I think so)



Tests:

 

[Dan_P]

Tank Overview


Hi everyone,

I’m looking for some help and insight from the community to troubleshoot a few persistent issues in my reef tank. Here’s an overview of my setup:


System Details

• Age: 8 months running
• Display Tank: 80x40x40 cm (~128L)
• Sump: External ~40L
• Lighting: 2x Spectra Knight V3 + Maxspect Etherium (some LEDs might be burnt, but overall PAR coverage seems okay)
• Return Pump: Dymax 1800L/h
• Skimmer: NY 300 (Brazilian brand)
• Wave Maker: HSBAO 4000L/h with controller
• UV Filter: 32W Ocean Tech UV with 500L/h pump
• Temperature Control: Heater + fans managed by a temperature controller (kept between 25.5–26.5°C)
• ATO: Gravity-fed freshwater reservoir (with float valve)
• Other Filtration: Activated carbon and Purigen used occasionally
• Feeder: Automatic feeder using New Life Spectrum Ultra Red pellets

Livestock

Fish:

• 1 Clownfish
• 1 Firefish (currently in sump)
• 1 Midas Blenny
• 1 Aurora Goby
• 1 McCosker Flasher Wrasse
• 1 Yellow Coris Wrasse
• 1 Royal Gramma

Inverts:

• Assorted hermit crabs
• Assorted snails (including 1 Astraea)
• 1 BBT anemone
• 3 shrimp (Stenopus gold, Cleaner, Dancing shrimp)
• Several brittle stars
• 1 Urchin

Corals:

• Zoanthids
• Torch corals
• Trumpet coral
• Mushrooms
• Goniopora (some thriving, others declining)
• A few SPS
• See more at the pictures

Feeding & Dosing

• Fish food: Tropical and new life flakes/pellets once per day (increased quantity recently)
• Coral food: Pellet coral food twice per week
• Additives: Power Elixir twice per week
• Bacteria: Delta Fish live bacteria
• Phosphate: Dosing 0.2–0.4 ml/day of Colombo Phosphate+
• All-for-Reef: I stopped dosing over 2 months ago because my KH was staying high

Main Issues & Questions – Help Appreciated!

1. Persistently High KH (Above 9)
   • My KH has been hovering around 9–9.4 for the last 2–3 months.
   • I stopped dosing All-for-Reef over 2 months ago but the KH still won’t drop.
   • I’ve done significant water changes and still no decrease.
   • Any idea why KH won’t come down naturally?
2. Phosphate Reading Zero Despite Daily Dosing
   • I’m dosing Colombo phosphate daily but still reading zero phosphate.
   • My corals (especially torches and two gonioporas) show signs of stress — tissue slightly retracted.
   • Could this imbalance (high nitrate / zero phosphate) be a major stress factor?
3. Nitrate Levels High
   • Using Colombo test kit (max reading is 4ppm), I had to dilute the sample to get a reading around 12ppm — maybe even higher.
   • Is this imbalance (high NO3, zero PO4) affecting coral health, and what’s the best course of action to restore balance?

Other Context & Past Issues

• I’ve dealt with dinoflagellates before — now running UV 24/7 as part of prevention.
• I’m currently battling vermetid snails (sessile worms in tubular shells) — they irritate some corals.
• Hydroids also persist — I dose fenbendazole in long cycles.
• Recently, a lot of sponges have appeared — I suspect silicates are leaching from some component (possibly plastic/acrylic in the sump or tubing).
• Some corals seem happy (most mushrooms, some gonioporas), but others like torches are retracted, and two gonioporas are dying.

Any thoughts, experiences, or recommendations are very welcome — especially on managing the KH/PO4/NO3 balance, and ways to reduce silicates and vermetid snails. Thanks in advance!

Photos and tests:








(Zoas with sponges, I think so)

7

Tests:

There does not seem to be an emergency here. Nitrates are fine. Dose more phosphate to raise the concentration. 9 KH doesn’t seem all that high.

 

[zoroi]

Thank you, that makes me feel a bit more at ease knowing it’s not an urgent emergency.


However, I still think this nitrate/phosphate imbalance is stressing some of the corals, and the high KH seems like a real issue, especially because it just won’t go down over time.

Any idea what could be causing this? And what steps should I take to fix it?

 

[Randy Holmes-Farley Verified Community Expert]

9 dKH is fine. It’s my target for my tank.

Nitrate is fine.

Feed more or dose phosphate to raise it.