Nitrates

[Tim leming]

My son and I have 5 tanks and all 5have really high nitrates 80-160 according to API master test kit . The one tank has a a sponge filter that ran 3 weeks in a cycled tank . Nothing else in it and it tested 160 for nitrates . Did 98% water change and next day tested  between 80-160in nitrates . Any ideas on what is causing this . Well water is testing 0 nitrates . Thank you for your help.

[Hobbit]

So in the other four tanks, there’s literally nothing in them? No gravel, no filter, no plants—just water? 

[Roko]

More informations would be helpful. 

Stocking?

Plants?

Ammonia in well water?

Some photos?

[tolstoy21]

Try a different type of test kit to check that the one you’re using isn’t bad or that your using it correctly. Try a dip strip and see if it’s in the ballpark for what the api master kit tells you.

And more setup details will help people help you better.