You can build a very cheap refugium using plastic bins and a florescent light form home depot. Cheap refugiums are genrally not so aesthectical but you could hide them.
Refugiums are a cheap and easy way to get nitrates and phosphates way down and eventually this will be necessary for a reef tank. It is quite possible to build a sump/refugium that has a very low probability of flooding. Look at some the suggested designs above.