New 60 Liter Tank Almost Ready

C'mon Chris - you know this is nothing like enough info!!!!

What fish have you got planned - eh? eh?

I'd be wary of Penguin tetras in a tank that size. They grow considerably bigger than is often stated. The Think Fish profile gives an average of 4 cms, with max of 6 cms, but that is certainly too low. I'd say an average of 6 cms, I have one which is a good 7 cms. They take a while to grow but final size is a lot bigger than the ones you see in the shops. Seriously Fish says " Expect it to reach at least 2.4″/6cm, with 3″/7.5cm not being that uncommon." which I think is much more realistic. A small shoal would use a lot of your capacity. I don't really consider them to be a small tank fish.

While an oversize filter may theoretically mean you can add more fish, that only refers to the filter's capacity to deal with the waste. You also have to consider whether the fish you choose will get along when they are more crowded together.