Unfortunately there is no such thing as budget when it comes to marines. There has been many a post from those who think that the 'nemos' look good and want to have some in a tank. They buy or acquire a sub 200l tank and try and set it up for marines.
Small tank does not equal small cost for setup, and in reality the money spent to set up a small tank set up incorrectly, then adding or upgrading gear as you find it does not do the job is probably better spent on setting up a 200l+ tank properly in the first place. Many attempt a small tank and then give up after they suffer fish and invert/coral losses due to an inability to keep the parameters stable, the temperature low over the summer months or sub optimal lighting.
I am not trying to put you off, but marines are something that you have to be willing to commit a fair amount of money to in order to provide the best conditions for the inhabitants, once you have achieved this, then they are a pleasure to keep, and not a chore.