My guppy regularly escapes at night and I find him on the floor in the morning. It's become a recurring thing, even with a lid on. Why does he do that? Is this a common problem or should I check something in my tank?
The most important thing is to check your water quality, especially ammonia and nitrite levels. Guppies jumping around like crazy at night is usually a sign that something's wrong in the tank. Stagnant water or water that's loaded with waste drives them completely nuts and they try to escape. I'd say it's pretty common in stressed fish, but it's always a warning sign you shouldn't ignore.
Also check your filter - if it's not powerful enough or if it's clogged, it creates dead zones in the tank where oxygen is lacking. Guppies love that for breathing and if it's not enough at night when everything's calm, they panic and try to get out. How many guppies do you have and what's the volume of your tank? It's possible they're just overcrowded, which creates stress. Even with a lid, you need little air gaps - maybe your lid is too airtight and that adds extra pressure.
Then jumping behavior also happens when there are potential predators at night (another aggressive fish) or just bad temperature. Guppies prefer between 22 and 26 degrees. Do a proper water test if you can, or at least do a partial water change every week. Often just a few regular water changes are enough to calm them down already.
Guppies jumping out of the water at night is often a sign of stress or poor conditions. Before you stress yourself out over water parameters, first check if your lid has any holes or gaps where it can slip through - even a small crack is enough. A panicked guppy will find any opening. Also make sure you're not just finding it dead and dried out but actually watching it escape; if it's really happening repeatedly and it survives each time, a tighter lid should do the trick while you sort out the water.
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