I did plan on creating a curb, perhaps 4" so it's not a huge step if I want to walk in there. The purpose of this thing is not to contain a major catastrophe, it is going to be intended for more of a barrier that catches spills for the most part, if I'm working on frags, if I trip & dump water out of a bucket or container, something along those lines. There will be enough electronic redundancy to where even in the event of failure (aside from tanks splitting open) I don't end up with more than a couple of gallons on the ground. In any of these cases either I'm there when it happens or I notice it a few hours later, again there will be a lot of controller monitoring etc. so plenty of warnings & redundancy as far as the plumbing goes.
I'm basically trying to do this without sinking a huge amount of time into it. Closet footprint is 67x41 inch, by my claculations 2" of standing water is over 20 gallons which is an insane amount considering how it's going to be set up.
Can plastic not hold 1 or 2 inches of water for a short period of time?
10g was the biggest spill I've had with this size tanks which was RO/DI related, in this case that is all in the garage. Aside from that I've had a big spill involving the DT breaking, in which case this doesn't matter since DT is outside of the closet.