I found it useful to run a small bead of epoxy around the edge of the moat to seal it (just used a small disposable brush) and let it cure (doesn't have to be really hard - a few hours is probably enough). This seals the unavoidable gaps as the epoxy will run through the tiniest hole and once it has started to run, it will continue and you cannot stop it. That initial bead does not have enough pressure behind it to go right through but will set in the gap instead. I used this the second time I poured epoxy - the leaks were one reason why I had to remove the first attempt and start again.