A 3ft x 1ft x 1ft aquarium holds around 90 litres.

The bigger the tank the easier it is to look after too, as the water parameters are a lot more stable and water changes are usually required less frequently when compared to smaller tanks, providing theyre not overstocked.

I've heard lots of opinions about how hard marine fish are to keep compared to tropical fish, if you are prepared to put the effort in and do lots of reading/research before buying anything, and then spend the time maintaining it, you shouldn't have a problem whichever way you choose to go.

One thing for sure marine is a lot more expensive to setup, considering the price of coral and live rock, fish, RO water, salt, t5 lighting, and the sheer number of powerheads required to get the water flow required to keep a reef tank happy.

Cichlids arent great community fish as theyre very territorial, and require different water parameters to most community type fish due to originating from a different location around the world. Tiger barbs arent great community fish either as they tend to fin nip, you can minimise this by keeping them in a large group, they tend to fight amongst themselves then and leave other fish alone.