I have a 10 gal. tank and my female guppy is hiding behind the intake tube of the filter and sometimes lays at the bottom. The only sign of disease is clamped fins. The same is happening with my female Zebra Danio. What should I do? What medication should i use?

Unfortunately, clamped fins and laying around could be due to many things from poor water quality to internal bacterial infections to parasites. It's hard to diagnose even for people who have had tanks for years, at least without a microscope slide of a sick fish that was just killed for testing which I couldn't do myself (kill the fish that is). Have you tested your water quality for pH, ammonia, nitrite? What temperature is the water? What do you add to the water (dechlorinator, salt?). How often do you do water changes? How long has the tank been set up? These are some of the questions that can help narrow down things to consider. If you're not doing it already, I suggest adding aquarium salt at a tablespoon per 3 gallons to help treat whatever is wrong and perhaps MelaFix by Aquarium Pharmaceuticals (a natural antibiotic) or perhaps Maracyn by Mardel (erythromycin, an antibiotic). I myself am reticent to add parasitic-killing medications as they are poisons that can do more harm to the fish than the parasite in some cases (for sensitive fish, in soft water, and/or for the more toxic poisons). If you see any white spots, do treat for ick. I've used Aquari-Sol. I hope your fish recover, and I wish I knew more about fish problems to help you. If this board were more active, others could advise you but so far, few people participate.