Red tailed shark dropped dead?

[Mdsuave13]

So i have a 55gallon tank, dual 350 penguins... everything in my tank was fine, clown loaches, tetras, and plec0s all look perfect.

Yesterday my redtail (maybe had him a year, about 4 1/2" long) looked fine, great color, very dark in the front, very bright red on the back. I found him floating today.

The only weird thing i can think of is that yesterday i saw a bit of white fuzzy stuff (kinda looked like cobwebs) sticking to him... this stuff seems to be kinda growing on my fake plastic plants... i am not sure what it is.

What could this be attributed to? my tank levels looked decent, temp was 76-78 deg F, nitrates 40ppm(higher then usual) ph 5.4 (very much lower then the last check which was about 6.8) ammonia was .25ppm (never usually have ammonia, but i did recently add 3 very small lemon tetras about a week ago), nitrites 0ppm, did a water change (20%)

What could this white stuff be? His corpse didn't look eaten up or anything, so it was kinda odd to me. Usually the clown loaches or tetras will tell me with their coloration if anything is out of the ordinary.

Why did my ph drop also? what should i do to remedy this?

[Nautilus29]

correct me if Im wrong but isnt there a kind of algea like that?? Maybe Im crazy but I think I remember reading that somewhere.

Edit: maybe I was wrong It could be fungus I would do a water change and try to get all of that stuff out of there.

[Mdsuave13]

i was reading around and columnaris seems like the closest thing i could find to a disease that looked like it.. but the weird thing is that the fish died REALLY sudden, i didn't notice any wierd stuff, even with the other fish, and he is probably the most vibrant and well colored fish i had. I just think it was kinda strange...

[Bassfan]

nitrates and ammonia is high.

[OscarFan]

How long has the tank been set up.

[Mdsuave13]

ok, misprint on the top, the ph is about 6.0, not 5.4... must have spaced out there..

The tank has been set up for about a year and a few months. This is the first time since its been fully cycled that i've had any fish die for unknown reasons. (i had a fish get caught in a plant and die from being stuck)

I know the nitrates and ammonia are higher then should be, i did a water change and will do another water change in a couple days to try to lower them down.

All the fish seem fine, maybe it was a freak accident that the fish died.

[Hairback357]

I am not sure about this white stuff your talking about but I would guess your PH has something to do with it. RTS's don't do well in Acidic water. A drop from 6.8 to 6.0 would be pretty drastic. Even 6.8 is not ideal for the RTS. A PH of 7.0 - 8.2 is best. I am concerned about this white stuff you see in your tank. The RTS is a tough fish. I have always kept RTS or Black Sharks and I have never had a problem with one. Knock on wood. Even when other fish get sick they keep going. I would be concerned with your water and trying to figure out why it crashed.