I have a 3.5 ft long water tank, with all the general equipment in it. I have 6 goldfishes and a cat fish.
First iof all, one of my goldfish which is full white in color, first its tail fins got red, then the fins started to get torn, i did a 95% water change in the tank.
After that i am seeing minute small grey bodies (probably fungus) on all of the fishes bodies. Now all seem to have infected as their tail fins are also turning red.
I browsed the FAQ sections and every body is talking about the level of PH, amonia and nitrates. I dont know how to determine these levels.

Kindly help.

As I am very depressed and dont my little buddies to die.

Please help.

Hi Asif welcome to the board, how r you...Well tell us how many gallons of water your tank have, I think you have a lot of fishes in your tank general rule is 10 gallons per gold fish. This is why they are having fin rot. In other words your aquarium is over crowded kindly inform us full dimensions of your tank so we can calculate exact amount of water in your tank.
Love
Rafaqat

there are several types of testing kits available. some are simple strips, that you dip in your tank water to determine the levels of ammonia, nitrites, nitrates, and ph. there are also ones, in which you fill a test tube(included with the kits) and drip chemical reactants into the water, then you discard the water. they all have relitively simple to follow instructions, and are available nearly everywhere fish supplies are sold.

i have not as yet heard of a kit that tests for fungus, bacteria or parasites. i would venture a guess, that your tank is over crowded. your tank sounds like it would be in the 30-40 gallon range, which is ok for three or four fish. goldfish grow rapidly, and produce wastes just as rapidly, and require more water and space than some other types of fish.