I have 125 gallon tank. I will be putting my 9 rb in. Local pet store owner advsed me that the best filtration is to run undergravel with three power heads and possible a fourth small power head on bottom of tank for current. Said will keep tank clean wthout cost of constantly changing canister filters. Does this sound like good advice or does anyone have better set up for me. There are no plants in this tank and I have gravel for bottom.