I'm new to this thread and only just got into fish about 6 months ago. The wife just treated us to a 160litre tank to replace the 50l one we had. I was pretty good with the filter bacteria and always had a good level with low nitrates, amonia etc but with the new tank we've bought a Hydra 30 filter that doesn't use bacteria but some electrical means of filtration and it seems excellent. Apparently you can put fish into the tank within hours rather than a week or so waiting for the bacteria to populate. I'm now going to get the smaller version for my son's 25l tank. Anyone else it use one?