Suggestions for cause of recent changes in tank

Hi all

Background: 30ish gallon tank set up since June. Stocked with 12 pygmy cories, 5 julii cories, 4 pandas, 4 mystery snails and 5 ADF's. Fairly heavily planted. Lights on 8 hours a day. Feeding schedule is 3 days on one day off, fish get a combo of flakes/wafers/pellets/the odd bit of brine shrimp, and the frogs get bloodworms/daphnia/brine shrimp.

I've been testing my parameters using the API Master kit every 7 days and doing a 75% water change every 9/10 days. Parameters for each test have always been 0. Plants have also been growing really well with no browning or die off.

The past few weeks I've noticed this brown mulm-like substance on all my floating plants and the sand, I've been siphoning it off during water changes but it comes back within about a day.

I've also noticed a slight change in water chemistry - after 5 days since my last water change nitrite is now 0.25ppm and nitrate 5ppm. This has happened the last two times I've done changes, so I've done another big water change each time I've got these results.

My plants have started to brown and die off slowly, and I'm having a bit of a mystery snail baby explosion! I know that these aren't pest snails as the only plants I've introduced recently have been in vitro ones.

Any ideas on a potential cause and any solutions? Is it a case of overfeeding? I'm a bit worried as I go on holiday in 2 weeks for 10 days and previously wasn't concerned about leaving the tank but now I am as nitrite and nitrate are rising after just 5 days.

Have attached pics of the mulm-like substance I'm dealing with. Off to do another big water change now....

Also I don't know if this is relevant but I was originally using Seachem fertiliser, changed to API about a month ago before I realised that this wasn't such a great fertiliser so I ordered TNC Lite which I've just received. I don't know if it's a coincidence that my plants have been dying off since I started using API or if it's linked?

This won't answer the issues on mulm, but just one thing I thought of, so you can rule it out. When you do the large water changes, does the nitrite go down toward 0.0 again? I ask, because, being in the UK, the legal limit for nitrite in tap water is 0.50ppm (I think), and I, sadly, regularly get 0.125ppm (ish) out the tap and sometimes (but rarely) closer to 0.25ppm. I don't think this is your issue with nitrite, but worth checking, as tap water nitrite in the UK can vary. It might be 0.00 95% of the time and then it could be 0.125ppm one day. The water reports are supposed to give the max reading of nitrite in a year, so might be worth checking that if you want to dive deeper. If your nitrate is maxing out at 5ppm, that's excellent though.

AJ356 said:

This won't answer the issues on mulm, but just one thing I thought of, so you can rule it out. When you do the large water changes, does the nitrite go down toward 0.0 again? I ask, because, being in the UK, the legal limit for nitrite in tap water is 0.50ppm (I think), and I, sadly, regularly get 0.125ppm (ish) out the tap and sometimes (but rarely) closer to 0.25ppm. I don't think this is your issue with nitrite, but worth checking, as tap water nitrite in the UK can vary. It might be 0.00 95% of the time and then it could be 0.125ppm one day. The water reports are supposed to give the max reading of nitrite in a year, so might be worth checking that if you want to dive deeper. If your nitrate is maxing out at 5ppm, that's excellent though.

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It does go back to 0ppm, I must be very lucky as I know some users get readings of about 40ppm from their tap water!

Just finished my water change and removed 32(!) baby snails. Maybe more, I was starting to lose count by the end.

More data on the issue will help. First light, what is it, how long, what spectrum? Second fertilizer...elsewhere API has not received as good a mention as others, I used Flourish Comprehensive and Flourish Tabs and had amazing results for over 10 years. TNC Lite should be as good, others have said so I from what I can find out I don't disagree.

What is the GH? How long is the light on?

Lcc86 said:

after 5 days since my last water change nitrite is now 0.25ppm and nitrate 5ppm. This has happened the last two times I've done changes,

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Do you know whether your water company uses chlorine or chloramine? I ask because I found this a few years ago in a Drinking Water Inspectorate report.
Nitrite may be formed when chloramine is used as the residual disinfectant to maintain the microbiological quality in the distribution network.

Byron said:

More data on the issue will help. First light, what is it, how long, what spectrum? Second fertilizer...elsewhere API has not received as good a mention as others, I used Flourish Comprehensive and Flourish Tabs and had amazing results for over 10 years. TNC Lite should be as good, others have said so I from what I can find out I don't disagree.

What is the GH? How long is the light on?

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The light came with the tank, its 17w/1800lumen, says temp 6500k (although I'm unsure what that means), on for 8 hours a day. I don't have any other info on the light unfortunately.

I've only been using the TNC for 5 days, I was going to finish the remainder of the API bottle but now that the plants are browning I swapped over to see if it helps.

Essjay said:

Do you know whether your water company uses chlorine or chloramine? I ask because I found this a few years ago in a Drinking Water Inspectorate report.
Nitrite may be formed when chloramine is used as the residual disinfectant to maintain the microbiological quality in the distribution network.

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This is a screenshot from my water supplier - gH is 9.2, it mentions chlorine and monochloramine as well.

They say they add a small amount of ammonia to make monochloramine but it sounds like they mainly use chlorine. I suppose it's possible the nitrite could have come in with the tap water but I would have expected any nitrite in your tap water to have been converted to nitrate pretty quickly if it was in the tap water.

Finding nitrite 5 days after a water change suggests that it's being made in the tank and the only way that could happen is from ammonia. But your ammonia level is zero

Essjay said:

They say they add a small amount of ammonia to make monochloramine but it sounds like they mainly use chlorine. I suppose it's possible the nitrite could have come in with the tap water but I would have expected any nitrite in your tap water to have been converted to nitrate pretty quickly if it was in the tap water.

Finding nitrite 5 days after a water change suggests that it's being made in the tank and the only way that could happen is from ammonia. But your ammonia level is zero

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Yeah I'll do another water test tomorrow and upload the pictures to see if there's any change in the ammonia, but so far I've only seen rises in nitrite and nitrate.

The rise in nitrate is probably from the nitrite, but the question is where's nitrite coming from?

Lcc86 said:

The light came with the tank, its 17w/1800lumen, says temp 6500k (although I'm unsure what that means), on for 8 hours a day. I don't have any other info on the light unfortunately.

I've only been using the TNC for 5 days, I was going to finish the remainder of the API bottle but now that the plants are browning I swapped over to see if it helps.

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Spectrum is the Kelvin number, and in the range of 5000K-6500K is just where you want it. So that brings us to the duration. Given the photos, I would reduce this down to seven hours. Just one hour, this can make quite a difference.

Changing fertilizer may take more than just a few days, but stay with it. I just checked again, and the API Leaf Zone appears to only have iron and potassium. Potassium overdosed is not too problematical, but iron certainly is. The TNC Lite has both but in proportion with everything else, and if you look at the label there are a lot of nutrients involved.

Thanks both, I've adjusted the timer so from tomorrow it'll be on for 7 hours. Is it worth reducing food as well? I don't feel like I'm overfeeding as I feel I would've had issues before now but could give that a go?

Checked ammonia just now and looks okay to me. Will keep checking daily to see if it increases.

Checked ammonia, nitrite and nitrate again today and all 0. Going to keep checking daily. I removed another dozen snails today, which makes me think I must really be overfeeding because I've removed about 45 snails in the last 2 days, albeit juveniles.

I know when I target feed the frogs they sometimes miss bits and the fish hoover up anything that's left so I might try reducing how much I feed. I've had some new java fern-lets grow so at least that's one good thing!