Sick Silver Dollar?

[finchfarm]

I was looking at my fish last night and noticed that one of my smaller Silver Dollars (about three inches long) has a cloudy-like spec on his pupil, his other eye is fine. None of the other fish, including two other Silver Dollars, have any problems with thier eyes.

A few weeks ago we bought two new fish, a Needlenose and a Bronze Cory. Both died within 3 days (the Needlefish had a cloudy eye). When the two new fish died we checked our water and did a full test panel of pH, nitrate, hardness, ammonia, ect. All our tests indicated that our water was prefectly fine. When we took the two dead fish back to the store to get a refund they told us we needed to test our water. We told them we already had and everything was fine. They said that sometimes the test kits can go bad and that we should bring water in to get another full panel test done just in case our kit was bad.

We went and did a few errands, went home and got a water sample, and took it to a different store to have our water tested there. They said our water was perfectly fine too. Since they said our water was fine we bought some new fish (Neon Tetras and Jewel Tetras), all of which have since died. We also had a Red-eye tetra die this morning. When I noticed last night that the Silver Dollar had a cloudy eye and that we had another dead tetra this morning, I tested the water again. Once again, our water is fine.

Does anyone know what the cloudy spec on the Silver Dollars eye might be and how to get rid of it?

 

[-germ-]

Likely causes...

Eye-flukes; Unlikely when the deaths are taken into consideration. Parasitic treatment may kill off the larval flukes but fairly pointless as the eye damage will remain. I think it is not actually contagious but you should research this further.
Cloudy eye; Likely, considering the deaths and an absence of any mention of fugal symptoms i'd assume as a result of a bacterial infection. Very hard to pin down without other symptoms could be anything....
Pop eye; Interlinked with the first two.

All are likely to be a result of environmental factors. The second two are associated with bacterial infection. Could be interlinked with most pathogenic illnesses, viruses etc.
Could also be a result of a nutritional deficiancy (unlikely with sudden deaths) or chlorine damage (possible).... Is your dechlor in date?

I'd try treating with a good anti-bacterial and improving my tank maintenance routine, do you gravel vac?

 

[finchfarm]

Yes, we do have a gravel vac.

Adding dechlor and an anti-bacterial solution could probably be beneficial for the tank. Just one question about this......we currently have a Brown Knife Fish (not African Knife) in the tank. Is it safe to give the recommended dosage on the medication with him in the tank or do I have to knock down the amount of medication? I'd assume its the latter.

 

[-germ-]

You'd have to check the label TBH or check with someone who knows about knives....
I know nothing about them.
Anyway, i undertreat first time around just to ensure that the treatment is tolerated and no bad effects may stem from its use.
I've heard this is fairly common practice, especially when sensitive fish are involved.
If things seem fine but you need a second treatment then consider upping the dose.
Make sure you have good aeration, as i'm sure you are aware...