I have a blue gourami which I bought about 3 weeks ago. This guy has been floating near the top of my aquarium, and keeps blowing air bubbles every once in a while. (Rest of the fish are quite active) I have lost several fish in the last few days, which include one black moor gold fish (had a "rash" on the body), and one pink kissing gourami, two little gold fish (don't know why they died), and one red betta, which had a black coloring on the face? At the same time, there are several fish which have survived for the past few months, from my first batch of purchase.
I am at a loss to explain the mysterious "rash" and the "bubble blowing".
I am very prompt in changing water, and do it every 8-10 days, change about 20%. I could not get the water tested, but have been using filtered water. I do not use any chemical treatments. Have a few ornaments, such as plants, and a little house. My tank is about 28 gallons, and as you can tell, I am very inexperienced at keeping fish (started this wonderful hobby about 3 months ago).
Please help me save my pets!!!