I have 6 22l tanks that all have ten fry in them, erm but they are starting to smell pretty funky., what can I get to stop this bearing in mind that they are really tiny fish and I don’t what something to strong that’s going to kill them. Thank you.

Is it an earthy kind of rich smell,or leaning more towards foul,gag you kind of smell? If it's a bad one,then I think the best way to resolve that,is more frequent water changes.How often ,how much do you do for water changes?How often do you rinse the filter out with old tank water to get rid of the muck on it?How long has these tanks been running?

Only four days, but they really do smell. i have cleaned the filters, but is the water that smells, and is getting to be a foul gag you kind of smell, i have not yet changed any of the water but four days is not a long time, and if i dont find something that works soon, i am going to have to change the water almost every day.

Have the filters gone through the nitrogen cycle, because if not, it could be this.

Since these tanks have been up for such a short time,are you testing the params?22L's isn't very big,and depending on what you're feeding the fry,they could get bad in no time at all,especially with the heat wave that everyone seems to be going through.