[snowman]

I have a 30 gallon freshwater tank which has been running for about 1 year. At the peak I had about 10-12 fish in the tank,Gourami's, tetra's, pleco, albino cory's and now I am down to 2 albino cory's left. I change 6 gallons of water every weekend and for the next 2 days the nitrates are 0. But on the third day they start to rise and by the 4th day they are off the charts. I am using an API nitrate test kit. I have vaccumed the gravel, upgraded the filter from a Fluval 205 to a 305, new heater after I found the old one stuck on and cleaned all the decorations in water only. I just need a little advice as to what could be causing the nitrate jump so rapidly. I have also tested my tap water and it is fine.

 

[petlover516]

What fish do u have now?

 

[snowman]

I only have 2 albino cory's left.

 

[NursePlaty]

Anything die in the tank? I would just continue doing water changes since thats the only way to get rid of nitrate.