Yes - I've had closed loops on other systems of mine. The last one I had plumbed into the back and it worked great. Well I ran into the pipe (Not hard just nicked it) it cracked my glass from top to bottom! That is a concern also for me - more plumbing more possible leaks. I'm so tired of having water on the floor and that played into my selection also. At some time if I decided I can always change it and have a closed loop - At this time I have most of the parts and I might go with small closed loops on the Sea Horse tank. The infinity only uses it's own system - and you don't want any wires, pumps, connectors etc hanging anywhere in that tank.
All my tanks will have check valves added with unions built in. They will be changed out every year as part of my maintaince plan. This way I don't have to worry about flooding everything. My equipment will handle everything and no they will not be full but this will allow me to have them a little deeper than normal. We'll see how they work out but I know others that use them and they have worked great for them - but yes you do have to do the maintaince. One thing to note is that if they do stop working it will be in the open state and not closed - so this should not be a problem.
These are the ones I'm talking about
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http://www.customaquatic.com/custom...ndexid=pf-cv-tu