RocketSeason, I have a 180 gallon All-Glass aquarium that is not reef ready so when it came time to turn my aquarium from a fish only to a reef and add a wet-dry filter underneath the tank I had to add an overflow. I have addressed your concerns below.
1. Most overflows are gaurded with small openings that only allow water through and maybe something the size of a piece of krill (the occasional
nudibranch will get through too). So their is honestly no reason to worry about clogging. If your are extremely worried you could add a piece mesh pad around the small openings to gaurd against anything but water going into the overflow. It will also quiet the waterfall noise somewhat.
2. Having the siphon break has not happened for me since I setup the overflow. Most overflows come with two u-tube that syphon the water from the internal part of the overflow seperately so even if one syphon breaks their still one going and your return pump can only return as much water comes out of your tank so their is no reason to worry about flooding the main aquarium. This is also true in the situation that your return pump should fail.
Overall in my opinion if you don't want to get a new tank or drain your tank to drill and attempt to convert it to a reef ready the overflow will do you just fine. It will also allow you to setup your
sump and increase total water capacity which is always a good thing.
