That is a Tetra Whisper Ex filter, I have 5 of them and I love them, it looks to me like its a Tetra Whisper 20 which is meant for 10-20 gallon aquariums. If you like this filter then you can go buy a Tetra whisper Ex 30 which will help, and the filter doesnt need a lid, its up to you if you want one on or not. When you do a water change take the cartridge out and squeeze the filter cartridge out in the bucket of old tank water. I would do that every 3 weeks.
125g South American..