Have been considering setting up a marine aquarium to go with my coldwater and tropical tanks.How difficult is it to keep marine fish.
Any advice greatly appreciated guys.

you might want to try posting in the saltwater section

Salt water isnt hard if you know what your doing. I would personally do alot of reading, and asking ? first..... I read for about 6 months before I got my first tank and did alot of mistakes and still learning......

the most important part of SW is the water quality, they dont tolerate ammonia, nitrites or nitrates if your going into the coral or inverts

Thanks Koko .Not planning on keeping coral or inverts its fish for me.Going the store for some on thursday as tank all set to be occupied.
No doubt I will keep getting bigger and bigger tanks like I have with the coldwater and tropical ones even my betta has a 10g to himself.

its hard if your a begineer and all you want is fish. but if you study them and know what you doing its pretty easy.