In the summer, if you lack an air conditioner, you may find that the hood traps too much heat, causing dangerous spikes in tank temp. If you have a relatively small tank, you could create a porous, breathable, customizeable hood out of needlepoint sheets! They are plastic sheets with small to medium holes in them. They are stiff enough to retain shape, but bendable enough to trim and fit to your tanks. I use it for my bettas, and it keeps the water 5-10 degrees cooler in hot weather, and ~ 5 degrees cooler in more moderate weather.
My other hint would be to give your fish a thorough examination at least twice a day - AM and PM if it is easy for you. By knowing your fish's body, behavior, and color, you can detect health problems in thier very earliest stages, increasing the chance for sucessful treatment.