What could do this?

[sheldibridle]

I had 2 clown fish 1 yellow tang 1 powder brown tang and 1 black cap baselet. This all in 120 gal tank with 180 lbs of live rock.
my powder brown tang looked like he may have had ick but I was not sure and so did my one clown. I started treating the whole tank then the powder died and the clown and then all died. my coral all look good. I did a 25 gal water change when I noticed the problem and then tested the water. The Nitrite was .01 same with the Nitrates. The PH 8.3 and alk in normal zone. the amonia was a bit above 0. Phos 0 calcium 420-440. I recently had a crazy amount of alge out break so I got 2 snails to help my hermit crabs out. I suspect I was over feeding and cut back to every other day. Food consited of pelets and brine shrimp frozen the pack said to feed them every day that those brine shrimp had suppliments in them I also would use garlic guard in the shrimp I was told that this would aid in keeping ick away. Anyway I sure need feed back. Also I have no canister filter just live rock and a good protein filter.

 

[natan]

Yuor tank is simply not sycled properly (thins u get ammonia and nitite above zero). all it needs is time. by cutting down on feeding all u do is trick yuorself. bacteria populations need food and time to develop. a mature tank of this size with thaws same fish should handle heavy 3-4 times a day feeding without any problem.

 

[vittoria]

powder brown um very hard to keep in my opion. I have a cycled tank and all the right eqipment and i still think its hard. Not running a filter ? what kind of skimmer u running? I have also used kik ich and it worked pretty good .