Getting New Fish

Hello, not been on here much recently. Been enjoying my new fish!
Anyway, only about 50% stocked at the moment. The other specifies I want are neon green rasbora and a small Cory. I know the Cory need a mature tank (what is that in months??) the neon greens also seem to need a mature tank I seem to remember. Is this the same length of time, or are they talking about a cycled tank (I know fish shops don't tend to recognise the fish less cycle)
Anyone any idea how long I need to leave it before getting either of these?
Also I think there are two species of small Cory, dwarf, salt and pepper and Pygmy. They all seem to have similar requirements. Does anyone have experience of any of these?
Many thanks for reading.

Thanks dbaggie,
Yes I know it isn't the same, but I just wonder about the green neons, and if mature is what they mean!?
I think peppered  are different to salt and pepper but I am not 100% are yours very small? Ie about an inch? I think I've heard they are quite delicate and not so easy to keep, but I may be getting mixed up. So much info floating round in my brain!
Ok, I will bear in mind that I should be able to get a good feel for when it's mature. Nowhere near yet obviously!

Cycling just grows the bacteria needed to get rid of the ammonia made by the fish and the nitrite made from that. But our tanks also need to grow maybe hundreds of other micro-organisms and we don't do anything specific to encourage those in the way we add ammonia in a fishless cycle. A tank is considered mature once these other micro-organisms have established themselves. We concentrate on the filter bacteria as the fish would die, or at least get sick, without them; most fish cope with limited numbers of the other micro-organisms for the few months it takes to grow them. Some fish do seem to need these other micro-organisms; neon tetras are the most often quoted example. But no-one knows exactly why.

I have neon green rasboras and mine are thriving. I had them just before I swapped tanks. I did have the water, decor and filter from the old tank but I used brand new sand and I lost the biofilm with it's micro-organisms on the glass walls of the old tank. A sort of half mature tank. I also do a 50 litre water change on 180 litres a week, which is 27%.
I did lose a couple when I bought them, but they were the ones that looked a bit iffy anyway. And one has even survived being sucked up during a water change, then jumping out of the net onto the floor when I fished it out 

There are three dwarf cories. Pygmy (Corydoras pygmaeus) salt and pepper (C. habrosus) and C. hastatus. Peppered cories are C paleatus and are indeed bigger than salt & pepper cories.

Thanks both.  I'll wait a few weeks anyway as I want to make sure there are no problems with the tank and fish as they are now. Think I need to get some floating plants next, to encourage a bit more swimming nearer the top of the tank.

I have pygmy cories. They are bigger than you saw, about 2.5cm. Yes they do swim in the water column more than some species but they also hide a lot, and I've read that from other people too. Make sure they have things to hide under. Though thinking about it, my ember tetras were never happy in the 50 litre tank either, they hid behind something all the time but since I moved them they are all over the place. Perhaps the tank gets too much movement past it with being in the kitchen and pygmy cories maybe don't like that.
I feed them sinking pellets rather than let them have left over flakes - though they will eat any flakes that make it to the bottom. They are not vegetarian; no cory species is. A popular misconception.
Not sure about the effect of the under substrate. Unless there is a lot of it and it's sharp, there shouldn't be a problem.

Well. my pygmies don't swim that much mid water. To be honest, they don't swim much at all  They are in the 50 litre tank in the kitchen and this is the same tank that the ember tetras swam in the same cubic inch behind a piece of decor. I think it's the place I have the tank, too much passing traffic for the embers and cories liking  The Sundadanios are fine in there though.

I'm afraid I don't know anything about rabbit snails, so I've no idea what temps they like   

do your leopard and zebra danio's shoal together nicely ?

Those two fish should be fine together as they are the same species 

They are the same fish tbh Chris, the leopards have been selectively bred to give that colour/form although there's not much info on the way it was done other than it was possibly done in Eastern Europe lol. You could have a good large shoal of them mixed as there's also a long finned version you can get but I haven't seen it as much.

Think they are a bit fast swimming for my small tanks, sorry forgot to mention, is a 40cm cube.
Come to think of it, maybe top swimming fish are fast swimming fish, so I'm not going to find any suitable for my tank?

Yep - any slow fish that swims at the surface is gonna get eaten. Not a good survival strategy!

The only surface fish that spring to mind are small, fast shoalers, and hatchet fish.... and they fly!