Aquarium cycle crashing from power cuts

Power interruptions are one of the most frustrating things that can happen to a cycling tank — when the filter stops, the beneficial bacteria colonising the media start dying off within hours, and you're essentially back to square one. Before we talk solutions, just so I understand your setup: what size tank are you running, and what fish are you hoping to keep in it?

That's a really common shared-house nightmare, and three crashes is genuinely demoralising. A 60 litre with tetras and corydoras is a lovely community setup — very achievable once you protect the cycle. The core problem is that most hang-on and internal filters rely entirely on continuous flow to keep the bacteria oxygenated and alive. Cut the power overnight and the media goes anoxic fast. Can I ask — are you using an internal filter at the moment, or something else?

That's actually part of the issue. Basic internals have very little filter media volume and minimal biological capacity, so they crash quickly when power drops. The fix I'd point you to is the Eheim Classic 250 external canister filter. It holds a much larger volume of biological media — sponge, bio-rings and substrate all packed inside a sealed canister — which means the bacteria survive significantly longer without flow than they would in a tiny internal. Aquarists regularly report their Eheim surviving 12-plus hour power cuts with the cycle intact, which sounds exactly like what you need. It's also whisper-quiet, very well built, and perfectly sized for a 60 litre.

That's the right question to ask. If it's genuinely every single night for several hours, even a big canister will struggle over time. So there are two things I'd do alongside the Eheim: first, label the plug clearly with a 'DO NOT SWITCH OFF — LIVE FISH' note, which sounds obvious but actually works in shared houses. Second, pick up a small bottle of Seachem Stability and dose it weekly as cheap insurance — it replenishes bacterial populations after any disruption. But the Eheim buys you enough resilience that the occasional overnight cut won't wipe you out the way your current filter does.

It has a bit of a learning curve the first time you prime it — you'll need to manually siphon to start the flow — but Eheim includes clear instructions and there are good YouTube walkthroughs for the Classic 250 specifically. Once it's running it's genuinely set-and-forget. Most people find it one of the least hassle filters they've ever owned after that first setup. For a 60 litre with corydoras and tetras, it'll be a very stable long-term home.