Angel died, wierd water specs

[The_Desacrator]

OK so last night one of my angels(Yogi) died. I checked the water and it was toxic(high nitrates, ammonia/nitrites were 0ppm, so i did a 75% water change. an hour later i checked the water again and the ammonia and nitrites were 0ppm, but the nitrates were already at like 20ppm.


The tank has 3 angels, a pleco, 2 bala sharks and a guppy. The size of the tank is 60gallon. I checked the filter cartridges(Marineland filters) and they were not that dirty.


Do you have any suggestions on what I should do?

 

[zparticle]

Just curious, have to vacuumed the substrate and mixed it up? I have a big pleco and I need to keep the substrate stirred up when I clean the tank to get as much of his poop out as I can.

 

[zparticle]

Also did you test the pH?

 

[The_Desacrator]

The substrate has been vaccumed and I did not check the ph.

 

[GNarnian]

Angelfish are really sensitive to pH changes in water. The last mini rain storm we had here in California ended up killing off one of my angelfish that was in my tank. The smaller the angel, the more susceptible they are. Sorry for your loss.