I have a 90l tank that currently holds 6 danios and 6 minnows. I also have two small snails although I think one is dead (it's in a separate bowl while I make sure I'm not getting rid of a live one but it's not looking good).
I fancy getting a few more minnows and danios to add to the shoal sizes and was told in a local shop I could get 3 more of each.
I don't want to crowd my tank but would they be happier with bigger shoals anyway?
Also what are the chances of them breeding? I don't want to buy some if there is a chance of the existing ones breeding and then have to get rid of some because my tank is too full.
I think I'd leave it as it is, 3 more of each would be pushing it. Bigger shoals are only better if they have enough space- overcrowding can cause issues with water quality and behaviour. Minnows and danios both need a lot of space to zip around.
Minnows are quite likely to breed but the danios may pick off any eggs and fry they can find. So you're unlikely to get overrun but you might get the odd one or two.
It's not necessarily a bad shop, it's just I have a difference of opinion on stocking levels I like to err on the side of caution, plus I think tanks with too many fish look crap and they behave weirdly.