I've never been a huge fan of biorbs - very expensive and very little water water surface.

However, I have been offered a 30 litre one for £50. It's quite new. Owner is moving and doesn't want it cluttering up the new house.

I'm tempted as I wouldn't mind a small tank of guppies just to brighten up a corner. Would this tank be suitable?

I really want some corys as well as they are ridiculously cute. Could I keep 3 corys and 4-5 male guppies in a tank this size, or would that be a bit too much?

Any suggestions welcome (but please don't say betta, that's for another day).

Thanks!

You would be a bit over-stocked with 3 corys and 4-5 guppies. If you went with just the guppies, I think it would be a fine, cute little tank!

I don't really know a whole lot about the BiOrbs, though, so the filtering may not be adequate. I'd say that's a pretty good deal on the tank, though, I would snatch it right up!

If nothing else, you could put a couple live plants and some ghost or cherry shrimp in there, that'd make a cool mini-tank.

The thing to bare in mind with biOrbs is that an essential part of the (air driven) filtration system are the very coarse stones that make up the substrate (this is an essential part of the filter design as this is the only stable part of the filter as the chemical and sponge cartridge is removed and renewed every 6-8 weeks - the stones are where the biological filtration takes place as water is drawn through them). The surface area is huge and is host to beneficial bacteria which colonise them. The stones are VERY course and as such are not really suitable for catfish such as corydoras whose delicate barbels may be damaged on them. I'd go with 4-6 colourful Guppies (probably just males!) that would look great and a 30 litre biOrb would make a nice home for them too

I thought I might be pushing it with the corys but can you blame me? just male guppies it is then, assuming I get the tank.

I hadn't really realised that about the filtration system - I've not seen the tank yet and never really looked at them in stores. So are they easy to clean? Vacuum the gravel, water changes etc. They've always looked hard to handle, put plants in etc. And the filter is simply a case of removing one central cartridge and replacing it?