have a est.55gal tank. hand full of guppies 1 lg pleco use a 70gal three stage filter w charcoal ..ammonia rounds and sponge i also add some fiberfill to catch the poop.have a fairly good idea about beni bacteria change filter in stages..have been doing 50%water changes weekly if not bi weekly for 3mo with little success. I have a underground filter system which isn't hooked up ..i vac. the gravel with each change.recently vac one side of filter underneath.. lots of yuk came up..unsure if yuk was beneficial or not .could the underground filter be the problem?did have it hooked up for a short while but my air pump didn't seem to handle it well.have air strip entire length of tank.i have been using the strips to test water..have hardwater 0 nitrites ph 6ish kh is 40 feed1x day with2 algae tabs..I change filter 5 to 6 week intervals 1 stage at a time and add water cond. with water change..guessing why the hardness..SOOO FRUSTRATED has only dropped to @160..getting rid of underground filter do the trick..and would I have to start as a new tank from square one?? I added a couple of sword plants and another plant which is kinda pointy in a pot.