Justin N

I have had my 75 gallon tank up and running with fish since about the new year. I have 4 small clown loaches, 11 small tiger bards, 1 small red tailed shark, 1 chinese algea eater and 1 8" regular pleco. I have a black sand substrate with a large power bio wheel filter, water temp constant at 79 degrees (F), my pH runs a bit high at 8.2, my nitrates are at 20, and nitrites are between 0/.5 i also have a small turbo pump, and two air pos to get a bit more water movement for the fish. I change 15 gal of the water every week changing one of the two filters out every two weeks. I feed them 1 time a say with flake food, dried brine shrimp and algea plates, about once a week using frozen brine shrimp.
Until tuesday everything was fine, i had started to get a little bit of brown algea growth on my plants so i decided i would be a good idea since the fish are all starting to get a bit larger to rearrange the whole tank and clean all the plants etc. I had noticed the last few times that i have changed the water that when i move the sand with the gravel vacuum there appears a cloady (yellowish/greenish) substance. I figured that was from when i was over feeding the fish and what not, which is part of the reason that i decided a cleaning was necessary. So in moving and removing everything thewater became very cloady, i did a 50% water change to try and remove some of the suspended cloadiness, it didnt really work.
The fish were all fine, then within about 90 minutes all the tiger bards and the red tailed shark were dead, within the next couple hours the clown loaches, and algea eater were dead, but the pleco lived.
I am not sure what exactly happened, and i dont really want to restock until i have everything figured out, and corrected.
i was reading that with sand they can trap gases which i thought might be a cause. others recommend to uses a certain type of snail, but the clown loaches will hunt them and eat them no?
And i know with the pleco my tank would eventually become overstocked, he is only a temp. resident, i rescued him so someone wouldnt try and flush him.
Any thoughts would be most helpful.

Toxic

Sounds like you have not been cleaning the sand. I would use a gravel cleaner to do this. you may have released to much bio load into the water and had an ammonia spike. You need to test ammonia, nitrites, and nitrates. Also I would not change my filter that often. You can loose your cycle if you clean to much at one time.

dvc_r

Welcome to fishlore...

In my opinion, your water parameters are not too bad, all though some may say your ph is a little too high and nitrites should be 0 (not .5). and 20% water changes every two weeks may be increased to 30-40 % every 3-4 weeks. But since you haven't had any problems in the last few months, I would definitely narrow it down to something during that one water change.

When you do the water changed every two weeks are you just replacing water or are you vacuuming the gravel? Built up gases happen when waste and food rot on the bottom of the tank. If you are vacuuming during the water changes I would lean toward "Contamination". Either some kind of residual (maybe soap or bleach) on the equipment or your hands. I did that once, I didn't scrub my hands enough after a day of working with pesticides!

One other thing: I'm going to assume you first add some kind of water treatment but is the water close to the same temperature when you add it. Or do you leave it to distill for a day or two?

PS: DON'T put snails with clown loaches!!!!

Shawnie

welcome to fihslore justin!! sorry for the loss of your fish...
sounds like a combo of a few things....first, by changing out the filters so often, and cleaning everything so much, the tank keeps going into a mini cycle..hence the nitrites and brown algae (probably diatoms the new tank algae)....what test kit do you use? the filters can just be rinsed in used tank water once a month and be fine....second, stirring up the sand could have caused some deadly gasses as you thought (I think methane) if the sand is too deep and isnt stirred up every couple weeks...as fast as your fish passed, id say it was some gas issues under the sand

IIIHawKIII

"fish PASSED, id say it was some GAS issues..." that was funny. not funny that your fish died. just funny how it was stated.

i agree with the others, if you haven't been vacuuming the sand, it probably let a bunch of stuff out when you finally did and the gas/ammonia spike zapped them. again, sorry you lost your fish.

agabr123

hi and welcome

you've gotten great advice above, i'm sorry you lost your fish

MizRamzi

Hmmm I'm kind a wondering how to vacuum my sand without sucking it all up

AlyeskaGirl

Awwww, I am sorry you lost your fish.