I have always had problems keeping plants alive in my 55 gallon tank. Very nice plants lose leaves, turn yellow, and eventually die within several weeks without ever gaining any type of root system. It's been such a problem that I have sometimes resorted to plastic plants but, of course, am never happy with the "lifeless" appearance of them. This problem has plagued me both with and without undergravel filtration.
Currently there is inert aquarium gravel on top of an undergravel filter measuring about 2" in the front up to about 3" in the rear. This gravel is covered with a 1/2" to 3/4" layer of the Seachem Florite. (The aquarium was already established with the gravel so, rather than start over, the Florite layer was added on top.)
The 150 gph mechanical/biological/chemical canister filter operates full time with a dual bio-wheel asembly on the filter output to improve oxygenation of the bacteria. Although this has an obvious biological advantage it's disadvantage is that it slows the water flow into the aquarium versus using an outflow pipe as the filter return. So, there are two power heads on the underwater gravel filter which provide good water flow and help considerably to keep the gravel clean.
The canister filter is cleaned and the media changed or recharged monthly. In addition, a 10% water change is performed bi-weekly with water run through an adsorptive filter. Electrolytes are added and the water is balanced for neutral pH before it is added to the aquarium.
Two weeks ago I installed a CO2 system (CO2 from Red Sea) and began dosing with the Plant Pack Fundamentals and the Enhanced: NPK according to the schedule provided in the downloadable .pdf.
It is the undergravel filter I'm wondering about. Will it's operation hinder root growth? Or, do you think the CO2 and the Seachem nutrients dosed according to schedule will make this a moot point?
It is so disappointing to bring nice green plants home from the store and then just watch them die over the next several months.