How to clear water after switching filter types
I recently changed from normal flow (power head sucks water up riser tube and discharges into tank) to reverse flow (Power head sucks water from tank through a cloth or foam filter and discharges the water and air down into the riser tube) in my 20 gallon tank and boy was it a mess. The change was easy but when I turned on the power heads they blew all of the sludge and detritus that was in the gravel and under the filter plate back into the tank making very muddy/murky water (I couldn't see more than two inches into the tank).
My solution to this was 10% water changes every two days and the addition of a power head sitting on a cloth filter (normal flow) to catch the small particles. I have had to rinse the filter media on this filter every couple days to get the sludge off and out of it. This has resulted in a chrystal clear tank in a matter of two weeks.
With reverse flow filtering the food and any other particulate will still settle to the bottom of the tank. Reverse flow oxygenates the good bacteria that lives under the filter plate to help the good bacteria break down the detritus and fish waste; it also helps get nutrients to plant roots as the water goes down under the filter plate taking the particles that create nitrite and nitrate down under the gravel and plant roots. Instead of the uneaten food and fish waste being sucked down from the tank through the gravel and filter plate it is sucked through the power head and blown out under the filter plate and is forced up through the filter plate and substrate back into the area of the tank you can see.
If I were to do this again I would have simply started running one type of filter system on a tank and stuck with it, what gave me the idea to change was a discoloration of water (yellowish tint) and some visible particles in the tank even though the water quality was in the parameters for a healthy tank.
With reverse flow the fish don't have to fight any current and I can run the power heads at an increased flow of air (the air line goes from the power head out of the tank and power heads will suck air as well as water), but by adding the normal flow powerhead on a filter I have created current and I run this power head to also suck outside air into the tank. This has oxygenated the tank and I can see the fish and shrimp seem healthier and more active.