Help with high nitrate

[Dorothy]

Hello, first posting. I have a 200litre reef tank, fairly well established, not too many fish, not overfed (I don’t think), but am struggling to get my nitrates to lower. It stays at about 50-70, regular water changes but still not coming down. Any ideas where I am going wrong? Don’t really want to add chemicals as had a bad experience previously, may of been heavy handed or just unlucky. Any help gratefully received.

 

[griss]

What brand/type of test kit are you using to test? Is it, by chance, expired?

 

[kfisc]

Without knowing a thing else, overfeeding is very often the culprit.