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I've been reading up on nitrite tolerance of fish. As with many things, the answers are complex and dependent on many things. Here's my situation:

Added 12 healthy 4-6inch Bluegill to my fully fishless-cycled 60 gal tank (40 gal heavily planted media growbed). Prior to adding fish, my system would process 2-4ppm of Ammonia straight through to Nitrate in 24 hours (in my case, a quarter teaspoon of powdered ammonia gave 2-4ppm).

Once the fish entered, ammonia spiked briefly to 2ppm, and has been consistently zero for days now. Nitrite jumped to 1ppm and seems stuck there. So it would seem that I am processing ammonia faster than nitrite, so I have a bit of "nitrite backup" perhaps. Note that I have not fed fish since they were added 5 days ago, so I'm a bit confused as to why nitrites are stuck at 1ppm.

My concern is the fish seem listless and are not eating at all (5 days now). My understanding is that days of nitrite exposure are bad - at any level. My water is clean, warm (72 degF), I clean up any uneaten food, bottom of tank is clean. Ph is good at about 7.0. Water is heavily aerated, so I believe DO levels are high. Growbed is super-healthy and heavily planted.

So, would a nitrite level of 1ppm keep fish from eating? Do I need to be concerned about the 1ppm nitrite - enough to start doing water changing?

Or maybe my fish are just tired of seeing me hovering over them :)

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Well I hope that your blue-gill make and that your bacteria catches up. Thought maybe you had done another water change or a partial one since Dec.14...

Does anyone know if Claude could sort of impact the nitrite 'spike' by exposing his water (probably easier with DWC, but maybe fish tank) to some light? Or does that only work with sunlight/ kill off some of the nitrite producing bacteria? 

Are you sure you don't mean nitrate is not that toxic.  nitrite is to fish kinda like carbon monoxide is to air breathers.

matthew ferrell said:

TCLynx-But his system isn't that new, and it has been cycling 2-4ppm tan to no3 in a day.  Un-feed fish are not going to be adding that level of ammonia.  At least I think they won't.

My bluegill were always very shy compared to other fish, and getting them to eat at first was a chore.  I mixed wild bluegill with farm raise hybrids, and the hybrids convinced the wild ones that pellets were good.  Since you moved them from another system that I  assume was pellet fed they should go back on pellets with relative ease.  I am always harping that fish do not need to eat like we do.  In fact, I stopped feeding catfish in the cooler months down south for 3-4 months, granted the water temps were low and therefore metabolism was low.  So going a week or two is not going to be a big deal.

BTW both folks above are correct.  0 is best, but depending on the fish species levels higher than that are acceptable.  Largemouth bass for instance can live in high levels(160-200ppm) because nitrites do not accumulate in their body.  Apparently according to this review paper bluegills are also insensitive.

Happy reading:

exposing the raft beds to sun is a trick the Friendlies uses and what it will do is slow down the conversion of ammonia to nitrite but this will cause a bit more of an ammonia spike along with the nitrite spike so you have to be careful.

If there was a lag in time between when the system was getting dosed with ammonia till the fish showed up, the bacteria can die back.  And 12 big fish in a 60 gallon tank even when not eating will still give off waste.  Remember that they excrete ammonia through their gills in respiration, not just as poo/pee.

good point. I did slack off a bit on adding ammonia just before fish added, so maybe the NOB died back too much. Too bad because they sure take a while to develop. If the fish can hang on I expect NOB to redevelop. That's my hypothesis at this point. Either that or its just too many fish for 60gal ( I don't really believe that).

Thanks TC. It was just a thought :), since Claudes says his ammonia has been at zero for days but nitrites are stuck at 1ppm...

Arghh...why can't I edit? I hope I said Nitrites stuck at 1ppm

Vlad Jovanovic said:

Thanks TC. It was just a thought, since Claudes says his ammonia has been at zero for days but nitrites are stuck at 1ppm...

I know many people are successful with fishless cycling, but it presents it's own set of risks as well. Well, maybe not risks, so much as strict adherence to the correct process.

Claude, you mention you don't really believe it's too many fish for 60 gals. From what you've presented, I respectfully disagree. In 6 months, probably even 3 months, you'll probably be right on.

I have some major issues with many of the spreadsheets, tables and rules of thumb for stocking density and feed rates out there. I just posted a similar comment on another site. My concern is that most of those tables don't specify anything related to system maturity. They just allow you to fill in the variable and then receive an answer as to volume required or quantity of daily feed, etc. 

Your system is re-cycling to some extent because the transition from fishless to fish wasn't ideal. That's ok, lesson learned and hopefully no dead fish. It will settle, but it's complete conversion process/balance has not found it's resting place yet.

I struggle when I read people posting that they want to feed 1 kilo of food per day to this many fish, in a tank this big, having this many GB's. All based on someone's chart and they haven't even broke ground yet. You've got to build up slowly to the aggressive stocking levels some folks claim are possible. Those charts don't always speak to DO either. it may very well be the most critical variable of the bunch. Regardless, optimum is better than maximum and remember optimum will change thru the life of your system with every harvest or introduction of new fish, etc..


Not only do people consistantly over-estimate the number of fish required to produce copious amounts of vegetables...


But, like Chip says... most are way over stocked.... and often ill-advised, even by some aquaponics "gurus".... as to stocking rates...

Try some archea

Claude, I have blue gills in two small tanks and I put them in before the tanks had cycled completely. (I got them in a pond just before the weater went bad) The fish in both tanks are very picky about what they eat. They hate pellets but love worms and also love chicken and pork. Pull it in very thin strips so it looks like worms.

My bluegills are alive and well, and getting more active. Water chem is fine. They are just starting to eat a little. They were used to pellet food (aquamax) for their whole lives, but perhaps some "real food" might work. I did darken the tank environment, since it was clear they really didn't like the light. And I do seem to have almost a 50/50 mix of males and females - maybe that is socially stressful??


Hi Claude,

Your call, but if you've got fish trained to eat pellets, I wouldn't veer away from that. Many struggle with getting their fish to even look at pellets.  

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