That is very sad to hear that. Don't loose faith just because your first try at it didn't work out. Did you have the water tested for phosphates, as the main contributor to algae problems is because of nitrates and phosphates. What I would do is a big water change maybe 50%. Clean everything in there that has signs of algae growth. When you start over and begin to see algae growth again clean it but make sure to leave a little. If you clean all of it out it will return worse, if you leave a little it won't grow as bad. Some people will actually leave the algae alone when they first start their setup as this will consume the nutrients in the water and the algae will die off as it consumes all the nutrients. What might of happened to your fish (which is not rare) is that if you don't have enough oxygen following though the tank. The algae when consume the oxygen in the water leaving the fish with no oxygen for them self and eventually will die off from lack of oxygen. You said your water is fine. There could be a lot of possible reasons why the fish died. Don't loose hope though. Even the best loose fish to. One more thing before you buy the fish your looking at ask the salesperson to feed them to make sure they eat good. they may give you trouble about it, that is to ensure they are well and eating right. Just because a fish looks healthy on the outside doesn't mean that he is heathy on the inside.