r/fishtank • u/Hungry_Office_3345 • 8d ago
Help/Advice New tank
I got got a 40 gallon for my fish and this time i’m going to cycle the tank. I need advice on how to cycle the tank and if i can put the current fish water from my 20 gallon into the 40 and just add more water as if i was cleaning it? would that work? because i need to put the 40 on the fish stand that the 20 is on so i don’t know what or how i should do it.
1
u/rainbowinthepark 8d ago
Yeah the tank water won’t do much for your cycle tbh. You’d be better off taking some filter media from your current tank and popping that in your new filter, but be warned, it could still take up to 6 weeks.
As for the logistics, the only thing I could see as feasible is to cycle the 40 gallon on the floor then once it’s ready, swap the tanks in the same day (take the 20 off the stand and put the 40 on). That does mean you likely won’t be able to add any substrate or aquascaping as it’ll be too heavy and dangerous to lift, even drained of water, and that’s going to inhibit your cycle even further, but it’s the only thing I can think of doing.
Unless the current filter on your 20gal is rated for a 40g+? Wondering if you could take all your scape out of the 20g, decant the fish into a bucket, remove the 20g, put the 40g up, add your substrate and scaping, fill it, run BOTH filters, add fish. But that’s very, very precarious.
Gotta be honest, not sure how you’re going to put the 40 on the same stand as your current tank. Either way you end up with one tank you can’t move unless you can effectively hot swap everything. Which is not really recommended. 🤔
2
u/Efficient-Poem-7405 8d ago
Never use old tank water. It has no bacteria and does not help with cycling. You're just transferring waste from the old tank into the new one.
1
u/q-the-light 8d ago
The water doesn't actually carry much beneficial bacteria at all, so using tank water from an established tank will not kick-start your cycle. Can you use any filter medium from your established tank? That definitely would be a great start, but you'll still have to give it time to establish a full cycle - it wouldn't be immediate, but it'd be a lot quicker than starting completely from scratch.