you could start your copepod population now and when you get a bigger tank just transfer the contents including the copepods.
Copepods are best grown in a sump so that predators cant get to them. But my LFS guy has a 75 gallon with no sump and he has a really fat and happy mandarin in his tank and loads of copepods that go scurrying around when the lights come on.
I seeded my tank 3 months ago with a jar of DT's copepods and now I have a like a gazillion of them. they are all over the glass/rocks, everything.
started a sump/fuge recently and they got in there without even having to transfer them, i found them in my cheato allready so they should start going to town down there too.
they eat phytoplankton so its a good idea to dose some phyto (DT's also makes this) to give them something to eat