The problem with an in-tank filter in a filled to the brimg tank, is that it creates surface movement that could also mean spillage. Even a bubble sponge filter creates surface motion. And a hang on the back isn't a nice tidy way to do it and spoils the effect. A canister filter is what I use on one of my large tanks, and I'll be getting another for my tank too.
Also, glass inlet/outlet tubes for the filter makes a hell of a difference to the look.
I guess you could have those problems if you buy the tank from a store...
but when you build it yourself it's because you hated something in it in the first place...
myself I hate the air pumps going hummmmmmmmmmmmmmmmmmmmmm I've tried shoving cotton in them..wrapping them with a pillow...forget it...
so my 2 in-tank filters for both my tanks were made by me...the 45gal has an overflow through some glass "teeth" over a glass box with holes half somewhere around the bottom...
when the water goes over the top and the "box" ...the speed/weight of it causes the water from the bottom to be pulled acting like a vacuum
works great but there's a couple flaws (to me)...small fish/shrimp can get into the filter once in a while....
which isn't too big a deal because they'll just be stuck inside the filter floss partition as the water in it flows down so there's no way out...
my smaller tank a bit under 10gal was made more for bragging rights...400gph turnover
with this guy I was thinking of making it for shrimp maybe nano fish so in this design I wanted highflow and 0 chance of shrimp/nano fish getting into the filter area
so i made the water flow into multiple holes upwards to about an of the top of sump wall...that partition has rocks blocking shrimp/fish from getting into it but allowing water to go through
then down/up/down into the filtration area then to the pump which pushes the water into a side open box with lots of holes to disperse the water movement
takes trial and error on the number of holes...basically fill it up..make it run..check if it flows back into the pump partition or if it overflows over the main sump wall into the tank
you could also seal the top of the return partition so no matter what flow you have it would always be pushed into the tank...the problem with that is...how are you going to clean it?
ps: the 400gph is the max without media etc...with media I usually run it at around 200-250 and my plants barely move and very little top movement
and the most important part (at least to me)....NO NOISE...no humming...no dripping...no water bubble "pops"
I'd like to see any non internal type of filter/sump type of filtration run without noise
