75g tank that has been running for 3 weeks. I seeded the tank with filter media from a friends established healthy tank. I have serveral java ferns, wisteria, wendtii, chain swords, hairgrass, anubias, etc, a decent amount of plants I guess. For the last 2 weeks water has been steady at 7.4 pH, 0 ammonia, 0 nitrite, and between 10-30 nitrate.
EDIT: No CO2 or ferts are being used.
last Wednessday I added 8 harliquin Rasboras. That evening, I noticed one was swimming around eraticly with its mouth always open. It died about 3 hours after I introduced them. By the end of the evening I had lost 3, and by the next day all but 2 of them. All showed the same symptoms, they would swim eraticly with their mouths stuck open, and had a whitish growth around their mouths.
I went back to the store where I bought them, and the manager said it sounded like lockjaw. He also said he thought the name was saprolegnia. He said there was no treatment, and if the remaining fish were ok after 3 days, it would be safe to add more.
So, I got home and got on the internet and found out saprolignia was a fungus. We started treating the tank with pimafix and melafix just to be safe after reading up on them on several web sites.
When Sunday rolled around, I went back to the lfs where I got the fisrt set of fish, but they had no harlequins. I ended up purchasing 8 harlequins at a different location.
So, Sunday I 10 harlequin rasboras. For two days they swam about, seemingly happy as can be while we continued the recommended doseing of melafix and pilafix.
Today I get home from work and there are 7 dead. the three that are remaining, 1 seems rather lethargic and just hovering about. The other two (which are the remaining ones from the first purchase.) are swimming about the tank seemingly normal, but all of them are opening and closing their mouths a lot.
I have two hang on the back filters and decent water disturbance, so I can't belive it is an oxygen thing.
Just tested the water, and just like it was last night, 7.4 pH, 0 ammonia, 0 nitriite, and about 10 nitrate.
What is going on? There must be something wrong with my tank to have 2 large die offs from two different sources of fish. I can't see anything wrong with my water parameters that I can test for.
Any help is more than welcome, I hate not knowing what I have done wrong to these poor fish and want to get it corrected asap.
EDIT: I introduced my fish to the tank by over the course of 2 hrs slowley adding a small amount of the tank water into their bag, and then netting them into the tank after the two hours was up. Their bag floated in the tank durring this time.
Edit 2: I just used some test strips I had lying about to double check. My tank is reading
pH about 7.4
hardness: somewhere between 300-1000
Alkilinity: around 180
I checked this against my tap water which I used to fill the tank, and it reads
pH about 6
hardness: between 150-300
alkilinity about 80.
I am thinking I may have a rock leaching minerals into the water. I am pulling it out and doing a water change while I wait to hear if anyone has any ideas.