I'll answer your first question by explaining a bit about filtration. There is mechanical, biological and chemical filtration. All filters perform mechanical, which is the forcing of water through various media to filter out particulate matter. This is the filtration that keeps the water clear [clear and clean are two different things]. One of the components of mechanical filter media is always some sort of sponge, pad, foam. This is the "fine" filtering. Biological filtration involves various bacteria and we primarily think of nitrification here, but that is just the beginning. There is also de-nitrification, and then we have the bacteria that break down organics. Biological filtration involving nitrification, which is the change from ammonia to nitrite to nitrate, occurs on surfaces in all filters, plus it occurs on surfaces throughout the tank, and primarily in the substrate. The substrate is also the primary place where denitrification and organic breakdown occurs. Chemical filtration involves the use of some chemical substance to alter the water chemistry, and here you can think of things like carbon; this filtration is almost always confined to the filter, because you have to put some type of chemical media in a place where all the water will pass through it.
A sponge filter provides excellent mechanical filtration, plus it provides a good medium for biological, with respect to the nitrification process. I use sponge filters in all my smaller tanks; my 10g has a single Elite sponge, my 20g and 29g both have a dual Elite, and my 33g has an internal mechanized sponge filter. My 70g, 90g and 115g have canister filters. I rely on the sponge filters solely for mechanical filtration. The biological occurs everywhere else on surfaces, plus the live plants use ammonia/ammonium. I do not use chemical filtration. Surface movement can vary, again it should depend upon the needs of the fishes.
Bonded ram pairs. If you observe a tank of rams for several minutes, without moving to disturb them, you should spot the pairs that have likely bonded. The males are easy to spot, as they will be continually challenging each other, usually with flared fins, head slightly down, charging toward one another. When you see one of these doing this, look for less colourful fish that are closest to the male, and sort of ignoring things. These will be females, and the one that remains closest to the male is likely one with which the male will bond. Give them plenty of time; consistent behaviour is the best sign.
Byron.
