I have had two kissing gouramis for at least four years. They have grown quite large. About two weeks ago I purchased a 55 gallon aquarium and placed two angel fish, 2 golden gouramis, four neons, two algae eaters, and a small shark in with my kissing gouramis. Yesterday morning I found one golden gourami dead. This morning I found the other golden gourami dead and when I returned home this evening, one of my kissing gourami was dead. The remaining gourami has something on its side that looks like a red pimple. Does anyone know what is causing these beautiful fish to die?