Upgrading to a larger tank

[ShellBell]

Yes, you can move them over. As you don't need the Juwel black carbon sponge, put them there instead. Leave them there for a couple of months then remove them - if there's more than one cartridge, remove one, then a month later the next and so on till they're all gone.

mg/l calcium is not one of the units used in fish keeping so we need to convert it into the two units that are used.
57.6 mg/l calcium = 8dH and 144 ppm. It is at the top end of soft.

This is fine for tetras and cories but a bit on the low side for endlers. I would increase the numbers of tetrass and cories once you are sure the new tank has settled but don't get any more endlers. Though I assume you have at least 1 male and 1 female is you've found a baby so there will be more

You assume correctly , is there something I should do to make the water more acceptable for them or would that upset the tetras and cories?

 

[Essjay]

There is no happy medium I'm afraid. If you 'harden' the water for endlers it will be too hard for the tetras and cories.

One of the experienced livebearer keepers on here has said that endlers are OK below the usual recommended hardness range, so i would leave the water as it is, but don't buy any more enders. Being livebearers the female(s) will have fry every month and some with survive being eaten so you'll still end up with more of them