
You have some monster fish there, are you making plans for a larger tank?
Looking at your statistics for this tank it is 190l or 50 gallons, all the fish you are currently keeping in there grow large up to 14", require good water movement and good filtration. Unfortunately the filter you have is only rated for a 40 gallon. This is part of the cause of your current tank concerns.
I would suggest adding an aquaclear 110 HOB to increase both the filtration and movement. This should also help the build up in the gravel.
