Hi everybody...first time here....great information.
I'm not a noob to aquariums, but having some issues that I'm not sure of the reasons...or solutions.
My tank is 90 gallons. It's been set up for 4 weeks with new water, substrate & filter media. I used pea gravel for the substrate with a little bit of sand left over from the previous set up. I tried one thing I've never done and that is driftwood. Being the tightwad I am, I went to the local lake and found a great piece that I scrubbed...but did not boil. It has not released much tannins to discolor the water. I've got just a slight tea color.
I'm running an AquaClear 300 with a sponge insert, activated carbon and BioMax.
After a week, I put some 'feeder' goldfish in to help cycle the water. At about 10 days I added in my 2 adult Sailfin Plecos, a Striped Rafael and an algae eater from my previous set up. They are doing great.
Over the next 2 weeks, 8 of the 10 goldfish died. They seemed to get a gill disease...puffy gills, heavy breathing and lethargic.
3 days ago I bought 10 tetras (similar to neon...but different breed) The next morning 3 were dead.
Still thinking that it is not my tank (water test results below) yesterday I bought 3 rummy-nosed tetras and a cory cat. This morning the cory is dead. :(
Water Test Results:
Ammonia: Just a shade above reading at 0ppm
I've been suspect of the driftwood, mainly because I'm inexperienced with it, and because I did not boil it. It looks great and stays clean looking. An odd thing about the dead fish is they look like they have been dead longer than they have. Their bodies are slightly fuzzy. Water temp is at 82 and I'm just now working to bring it down to 76.
I've done 5 gallon water changes about 4 times now. The water was very cloudy for the first 2 weeks, but is now very clear.
I know I want to get my PH down, beyond that..not sure what to do next.