So - went of to Ifs all excited about getting my 1st fishes.

The shop a few weeks ago recommended I buy 10 neons to cycle the tank - but I went for the fishless method instead.

I told guy yesterday I had fishless cycled my tank - but he said I still needed to only buy 10 neons/danios as otherwise he couldn't guarantee the fish against death.

I thought I needed to buy a few fish - I was planning about half capacity -to keep the ammonia levels up to keep my bacteria colony going??

I have since read that cardinals are not as hardy as neon tetras and should have an established tank?

Upshot is I now have 15 Cardinals - wanted 10 but 15 were caught so got that many. They all seem fine so far.

What do i do now.. how long should I leave it before I get some more fish?

Tank is 30gal

No-one told me you needed a degree in chemistry to keep fish

Ha ha i second that regarding the degree

After a statement like that, personally I would never accept any advice that person gives you regarding fish, ever. From my experience, and from everything I've read, I can think of few community tank fish that are less suited for cycling than neon tetras. Danios, on the other hand, are notoriously hardy.

Anyway, it's my understanding that if you complete a fishless cycle, you can add your entire fish load at once (once the cycle is complete).

Regardless, I would watch the ammonia and nitrite levels of the tank. If they seem stable for five days or so, I'd consider it safe to add more fish.