New member
I have an 8G tank that has been running for about 1 month and I cant seem to solve my Nitrate problem, i did a test last night and my nitrates were at 0ppm, this morning I did a test and my nitrates were up to 20ppm!

I have a Fuge in my second chamber that has the light on during the night from 8pm to 7am, I looked everywhere in the tank for any decomp and did not find anything, I do have PURIGEN in my second chamber under my Cheato and it has been there for 1 week.

If anyone has any ideas please let me know?

Sugar Magnolia

Mother of Dachshunds
Staff member
RC Mod
Have you done a water change yet? If not, do a 10-20% change, it'll help bring down the nitrate.


Black thumb reefer
Premium Member
Sounds like your tank is breaking in. Give it another week or so, and just keep doing small water changes. You will probably see an algae outbreak shortly, which is all part of establishing your biological filter within the LR.

Purigen doesn't remove nitrate, and you are probably not getting much out of it with passive flow in the fuge.

Do NOT start to stock anything at this point - when it reads 0, then go ahead. Adding livestock will compound your problems.


Premium Member
Nitrate is one of those things that will tend to accumulate in a cycled tank. It shows that the nitrogen cycle is working, but the system is having a hard time consuming the nitrate being produced by the nitrifying bacteria-- a very common problem, especially in very small tanks. With an 8 gallon, frequent water changes will be the simplest and quickest way to keep it (and all your water parameters) in acceptable ranges.