Help!!

[white specter crayfish]

Just did a 50% water change and the oscar is swimming around and begging again! I will monitor closely and do a couple more water changes over the course of this week. (the nitrates are down to 40 after the water change)

As for the Kh, I'll put some baking soda in tonight. Thanks!

great to hear your oscar is doing well

 

[duanes]

There is nothing wrong with a pH of 6.5, but a 0 KH means your water has no buffering capacity.
How big is the tank?
What is the level of nitrate coming from the tap?
Sounds like you need to do large, every day, or every other day water changes to reduce nitrate, as part of a normal routine, and to prevent the tank water from being oscar urine soup.