Just wanted to share the fact I needed a new heater and discovered KMart has a 50W heater for $12 here https://www.kmart.com.au/product/50w-aquarium-water-heater/2166314 .
I bought one to try, put it in and am very happy with it for the price. Where can I get a heater like that for twelve dollars and only a couple of blocks from home, will keep you posted. :)
They only have that size but if you need a 50 watter then I don't reckon you can go wrong.