Well Ive decided i want some cat fish, but i know little about catfish so i was hoping that somone could help choose the best catfish for me?
By default, you can't go wrong with a school of Corydoras. They're easy to keep, small, available in lots of colours, and widely sold.
my tank is 60cm by 30cm and i want plecs or loricariids becuase they eat away at the tanks algae dont they?
The algae-eating abilities of plecs are overrated and misunderstood. No catfish will keep your tank so clean you won't have to remove algae. If your tank lacks plants, it will quickly develop an algae problem anyway, and some forms of algae, particularly blue-green algae and red algae ("hair algae") aren't eaten by catfish. Moreover, as you add fish to the system, nitrate and phosphate levels go up, speeding up the rate at which algae grows. So by all means buy an algae-eating catfish species if you want, but don't feel like you have to. The reality is it'll make no difference to how often you have to wipe the glass with a scraper.
but what heat should i keep the catfish at, and which type should i buy??
Corydoras and whiptails broadly prefer low-end temperatures between 20 to 24 degrees C depending on the species. Some actually prefer even cooler conditions, for example bearded Corydoras (Scleromystax barbatus) which would prefer 15-18 degrees C. Only a few Corydoras actually thrive at high temperatures. Your standard plecs and bristlenose cats are happy at the normal 24-26 degree C range, while anything from the Rio Xingu will need slightly warmer conditions, around 26-30 degrees depending on the species. In other words, it will depend on the catfish in question.
I'd actually start by looking at what fish you have. If you have danios and minnows, these like cool water, so Corydoras and whiptails would be ideal. Neons also like cool water, so they're good too. But most other tetras prefer warmer water and will be better companions for catfish that thrive at around 25 C. Angelfish, discus and gouramis like even more warmth, as do Mikrogeophagus, so in those instances one of the Rio Xingu species would be a possibility, or a warmth-tolerant Corydoras such as Corydoras sterbai.
Water chemistry may be an issue too. If you were keeping livebearers, particularly Mollies, then adding salt to the water is beneficial. In this case, you'd want a brackish-tolerant catfish like Hoplosternum littorale or Hypostomus plecostomus.
Cheers, Neale