Yes this is my 29 gallon (my only tank). It has been up and running for 8-9 months. Today I cleaned the filter and did a 25% water change. I do a water change once a week and clean the filter once a month.
I have a Penguin 200 HOB filter. What I do to clean it is take it off the tank, put the bio-wheel, filter foam and ceramic beads in a bucket of tank water and wash them around to remove any debris, then take the filter body and impeller and rinse them in the sink.
Is my filter not big/"strong" enough for a 29 gallon tank with this many fish? I updated my signature for my number of fish.
the filter looks like it is plenty for the tank. though vacuuming is still just a general upkeep kinda thing (debris, large poops ect hehe)
do you have your water parameters?
the tank is sliiiightly overstocked but it isnt outrageous or anything but just the sheer size of Dgourami might be the prob. if its not biological