The filter looks like one of the model of Dennerle version for nano tank I came across in some websites. To answer your questions on my filter fountain DIY, yes it works as a internal filter with the chamber. I guess it did a better job than what I have now since have to replace the filter quite often. The way I did with the first attempt didn’t have to replace anything but it would take a bit some time for everything in stable but once it does, I don’t have to do much of maintenance. The mangrove roots helps stabilize the nitrites or ammonia very well if you have appropriate amount of them! Some shrimps even climb up to the fountain and like to stay there 😂 I don’t know if I can find an old photos of it or not. If I can find one I’ll post it here but the quality of the photo might not be best 😂