I don't hear alot of talk about undergravel filters these days.

Years ago they were everywhere and years ago used them and they seemed to work.

The question is then is there any merit in using them again? Would anyone recommend using one in a 100 litre planted tank with 12 Fish?

It's old tech now, with filters being far better at the job.

Oldies but goodies. I have always been a fan of them and they are quick, easy and cheap.

Sure, they may not be as good as the new newfangled fancy canister filters but they still do the job (and take up less room).

Just make sure you have at least 5cm of substrate over the plates, to give the plant roots plenty to anchor themselves in, and do not have any gravel burrowing fish.

Can't use them with sand :dunno: I have sand in all of my tanks because I keep mostly catfish & the occasional loach shoal. And for DSBs and plants. So I use sponge filters for breeders, HOBs for small tanks and canisters for anything over 100L for superior filtration (and though I have no sumps, sumps for tanks over 300L). So they don't really fit in anywhere for me - I'm new enough to fishkeeping to have never actually seen one in action, but my father apparently used to have one and hated it.