if you dont have the bio bale in there you can put just about anything else in. a heater would be fine. the bio bale doesn't actualy make high nitrates. what happens is the bio bale supports a very large amount of microbs and bacteria that take care of amonia and nitrites befor the live rock can get to it. but because the bio bale is in a high water flow area that has a large amount of oxygen, anerobic bacteria (bacteria that live in low oxygen areas) that change nitrates into nitrogen gas cant grow. there for there isn't anything to change that nitrate into nitrogen gas so the nitrate level will rise in your tank. this is fine as long as you do regulare water changes.
now if you take out the bio bale you need to do it slowly( take only a little out at a time) in a span of about a week or two. that way the bacteria on the lr
will have a chance.
so if you do take the bio bale out, be shure to have enough live rock.
hope this helps