Gold fish and heaters?

Question
ok i hope you can help me any information that you know off is kindly appericated. ok i had a scavge algea fish and he die a week after i got him know the pet store told me cuz it needs to be in warm water,ok so i bought a heater but gold fish water temp should be about 68* to 74* that is what i heared i just need to know if a heater is important my tank is 78* and 82* i know that is high and the heater is not even on? i just dont know what to do, what are good algea eater and can share the tank with good fish so neither of them will die? thank you for yur time

Answer
You definately don't need a heater for goldfish, but they will survive at 78 degrees. (they'll survive, but they wont't thrive). It would be a good idea to keep the goldfish cooler; in which case no algea eating fish is appropriote due to the cool & fluctuating temps. You can also use snails as an algea eating animal, snails can be kept at the cooler temps required for goldfish.
If the tank has a filter, then adding an algea eating fish is OK. Pleco's (plecostomus) get very large, and you possibly may want to reconsider that particular fish. In a heated and filtered tank, Chinese algea eaters, clown pleco's, and Otocinclus all stay relatively small, and can be kept in small aquaria.
Algea eating fish are useful because they eat the green slime that grows on the rocks and walls of the tank. They don't clean it for you, but sometimes they help.
I hope this helps,
Good Luck