Second tank

[Elena82x]

I'm wanting to move my fish from a 70l to 240l to allow me to keep the molly fry I have and add a few more fish. Can I just swap everything from one tank to the other and top up the water (conditioned) for it to be ready cycled? I assume that I need a larger filter and maybe stronger heater for the larger tank so to avoid stalling a cycle would I need to run it with two filters to start with until the new one builds up enough bacteria? I was planning to wait out a full fishless cycle but I think the fish are under stress in the current tank due to over crowding with the fry box taking space.
Thank you.

 

[Essjay]

If you intend only the 240, yes move everything over at the same time. With the filter, the easiest is putting all the old media into the new filter. Sponges can be cut up to make them fit. Then fill the gaps with the media which is supposed to be in the filter. After a month you could start replacing the old media with new, a bit at a time.

 

[AdoraBelle Dearheart]

It's not usually a problem if you move all the substrate along with the filter and everything else, since the substrate holds a lot of the beneficial bacteria. Or some people rinse the gravel in tap water since they're setting it up in a new tank, and lose a lot of the BB. Just be aware that if you do change out or clean the substrate in tap water especially, that the tank can go through a 'mini-cycle', so do more tests than usual to make sure ammonia and nitrites aren't spiking. If they do, large water changes will be needed, but a mini-cycle usually only last for a few days while the BB colonies catch up again!

Tip for doing the switch - It always takes longer than you expect it to. So for however long you think it will take, add 2- 3 hours on top of that! Is the new tank going where the old one was? Just wondering if you need to move the fish out into buckets or anything while switching the tanks out, or can move the stuff over from place to another, which is slightly easier to manage.