I have just bought this tank. http://www.aquariumsdelivered.co.uk/catalog/fluval-roma-125-aquarium-only-p-858.html It comes with a Fluval 3 PLUS filter, but nothing that will oxygenate the water. Having a under gravel filter would fix this though. i want to use a sand instead of gravel and the sand i have bought says on the bag "When used in conjunction with under gravel filters, a layer of filter matting is required below the sand." so i know i can use it with an under gravel filter. but are they worth getting? If so do you have to put the sand at a different thickness at the front compared to the back (not sure why i think that just in the back of my head) If not should I just use the filter it comes with and an air pump?