I'm thirding this! You can also guarantee that if something is gonna break, it's going to happen late at night or in the early hours when you can't just nip out and get a replacement. These things always happen at the worst times. My heater broke late at night in winter, tank dropped from 79 to 63 before I realised. I was lucky tank only had guppies at the time and they could tolerate it, but they weren't exactly happy either, and my LFS was closed the next day, so it took two days to prime a new heater.Yes, Eheim do make excellent filters but they are not quite as well built as they used to be.
I have two Eheim filters as spares as I am loathe to let them go!
But excellent tip from essjay as it’s always worth having spare impeller shaft as when one goes during maintenance clean its really and truly annoying and panic stations starts to sink in trying to get hold of one quickly from any LFS to get your tank back up and running again before too long.
Always worth keeping spares of anything you think is essential, spare heater, spare parts and even spare filters in case your current one goes klonk! You never know!
Now I won't be without a spare heater/filter/airpump, and if I had more funds, I'd have battery powered back ups too.