How to diagnose disease in tropical fish

[birnur]

We had our tank for close to a year now. It is a 28 gallon one. We have kept the number of fish to no more than 10 at a time. We did have some deaths but nothing that will make us think it was a disease. Recently we have lost two Mollies back to back and now a glow light tetra seems to be suffering from the same ailment. The fish starts acting weird, not being able swim flat, almost swimming in cricles and diagonally. They stop eating and then over a week or so get exhausted and very weak. We have noticed some silvery gray spots or scales on our red Molly's tail where it meets the body when it was struggling with the ailment.

We tried to remove the weird acting tetra today without any success. We decided to bring a sample of the water to the pet shop for a possible diagnosis tomorrow.

Any ideas what might be this disease/ailment?

[Billythefish]

Sounds like your fish have ich try this. Tern your temp up 82/86 add seasalt 1 teaspoon for every 10gal leave it four about a day then do a 40% water change and take a look at your fish the spores should be gone if not do the same thing again