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Ammonia in Baby BN Pleco Growout


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Hi All, so I've been getting ongoing Ammonia readings on my baby BN Pleco growout tank (20 Gal Long) that was set up on May 31.  I've been doing daily 50% water changes since June 5 when .25 ppm of Ammonia was detected. I'm using API Master Test kit and have been consistently testing every morning and getting .25 ppm Ammonia until today when I got 2 ppm Ammonia.  When I set up the growout tank, I transferred over a seeded medium Co-Op sponge filter as well as a seeded HoB (Dymax Slim Flo 240). The Dymax was on my 10 gal and I know it's small, but it was seeded and all I had at the time.  On June 15 I also put in another seeded sponge filter from an existing 5 gal plus a new AquaClear 20 HoB. 

I have been feeding heavily because there are 117 baby plecos plus their dad in this tank.  Way more babies than I initially thought.  I have been vacuuming out uneaten food and reduced feedings (quantity and feeding every other day instead of daily).  I also was reading in another post about false Ammonia readings when using Prime (which I have also been using), so I experimented with yesterday's water change and used API's Stress Coat as a dechlorinator.  This morning was a bit of shocker to see 2 ppm Ammonia.  I treated with a dosing of Prime to de-toxify Ammonia in the meantime. I tested the clean dechlorinated water in the bucket prior to putting it in the tank and it tested 0 Ammonia.  My tap is also 0 Ammonia (city water).

Pictures of the tank are below along with today's Ammonia test. I have seen no deaths and all babies and dad acting normally. No red gills, no labored breathing, etc.  My next plan of attack is to clear out the large rocks and driftwood and look for any uneaten food and continue with daily large water changes.  I've also been adding bottled bacteria (API StressZyme).  

Any other suggestions?  Keep riding it out with water changes?  

I have also added Amazon Frogbit from other tanks, but it doesn't do well in this tank. I have seen the babies rasping on it and it just looked ragged, melted and leaves stripped to the point of being see through plus it gets blown around in the flow from the HoBs and sucked up in the intake tubes.  I have tons more frogbit from other tanks I can add. As you can see the tank is hardly planted.  Just a spare Anubias, a section of PSO, frogbit, 2 marimo moss balls and some windlov java fern seedlings.


Other parameters:

Temp:  78 F
Nitrite: 0
Nitrate: 0 
PH: 7.6
Back wall of tank is blacked out with static background. Tank sits in my laundry room in front of a glassblock window. The clip on Aqueon light is only on when I do maintenance since the tank gets a good amount of natural light and faces west and doesn't have much for plants. 




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A few suggestions:

  • Double check to make sure that nothing is decaying in the tank and giving you the high ammonia readings. This could be a fish rotting under a rock, excessive decomposition of the wood, etc.
  • I would suggest maybe testing with another test kit (or strips). Sometimes test kits can go off (and the bottles in those do expire). 
  • Usually the filtration (bacteria) will catch up after a few days to manage the load, but with 100+ growing fish, it may just be too much. Have you considered adding a fast growing terrestrial plant to help suck up the nutrients? Pothos could be one to try. If you are worried about the fish nibbling on the roots, you can use a mesh bag or nylon screen material to keep the fish off of the roots. Pothos plants are usually around $10 at most stores, and can be an inexpensive way to help.
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Thanks @Zenzo for the fast reply. After work today I'm going to remove the large rocks and looks for anything dead/decaying along with water change, water change and more water change 😉. Only the frogbit has been looking limp and mushy so I removed the worst of it yesterday. I thought they could have been contributing.  My test kit bottles for Ammonia say they expire Feb 2026.  Testing my other tanks I get 0 Ammonia.  I have Co-Op Ammonia test strips and they read 1 ppm on this tank.  I forgot about the Pothos option.   I thought they suck up excess nitrates, not ammonia but am happy to try them.  I have mesh bags too and will definitely pick up some plants.  

I forgot to add that all the babies are an inch or smaller. They were born April 20th.

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