Well, I haven't done it...but maybe pick up the box & set it in their new tank & let them swim out. Like netting but much easier...
BUT make sure before you try it...Is the new tank cycled? Similar water parameters to the old tank? I would "steal" some of the old tank's filter media to put in the new filter. Maybe 1/4 - 1/3 at most. I forget what all you have in the old tank beside molly females but try to judge adult body mass to fry mass if that makes sense. 1 adult might = 20- 30 fry? Then test & change water as needed in both tanks. The beneficial bacteria can double in 24 hours so you shouldn't have to do it for long...
Yeah I was going to move media over as well as some of the water. Didn’t know if I should try to put them in a zip lock bag and then float it a bit? Going to be all mollie fry and then I’ll weed them out and then add angels to keep ‘em in check?
As long as the temp is within a couple degrees (say 2?) you don't need to worry. Skip moving the water as long as the parameters are close (test!). There isn't much if any beneficial bacteria in the water. It's on the surfaces like decor, substrate & filter media. You don't need the bother of moving water...don't forget the dechlorinator!...Maybe a couple live plants? They help with ammonia a little tiny bit & usually have beneficial bacteria on them unless they're hydropontically grown...plus they look nice!
Easy plants include java fern & anubias, almost anyone can grow them in any tank, any light. They are attached to wood or rocks, not planted in the substrate. They grow slow so less maintenance, a good thing! Plant enabling you! Try it!
My plan is to pick up the 75gal and set it up. Ac110, sponge filter and heather, and then add some water from the main tank that the fry are in. Adding a few crypts, driftwood and such since I grabbed the lowlight aqua sky light. Then adding the fry on Sunday morning.
hopefully this is coherent, had a few beers on this cold ass Friday night. Appreciate the insight!
If the used media you're moving over to the new 75g has been in use on a stocked tank for a long enough time, you will be able to stock the new tank immediately. Like said, transferring used tank water in a situation like this doesn't do anything for you.
I hear you on the cold. It's like 5degF this morning in the Buffalo area.
Fry do not create much ammonia. So if you have a bit of bacteria to start, the bacteria will grow along with the fry. Be sure to sponge the intake of the AC so fry cannot get sucked into the filter. Most of my grow tanks use air power and Poret foam cubefilters.
Live plants use ammonia (in its ammonium form). They also host nitrifyng bacteria. So if you put a decent amount of plants into the tank you do not need to worry about cycling. Nature will do all the work for you.
The above assumes only the fry will be going into the new tank. If other fish will go in as well at the outset, then be sure they are not fry eaters. There is a limit to how many fish you can add at the start using the above method.