Heck, I think I've done that three times in the last month. I set timers, then walk away and don't hear them. My next trick is going to be to plug the RO into a timer, so it shuts off after 30 minutes automatically. We'll see how that plays out.
In regards to the flooring... just my two cents on tile... (I am in construction, so take it for what it's worth.)
Fish tanks on tile place a lot of weight on a small area. If the tile is not perfectly level, you run into all sorts of issues. Likewise, the tank weight can easily crack a tile. There is a product known as an uncoupling membrane that essentially separates the tile from the actual concrete slab. It is by Schluter and called Ditra.
Ditra This is a cool thing because it allows the subfloor to expand and contract seasonally, without cracking tile. It also redistributes the weight of your tank across the whole floor. There is a thicker version made by Schluter that actually lets you run heat under your tile. Soooo nice on the feet.
Ditra Heat Naturally, like so many things in this business - this is the higher dollar solution.
Regardless of how the tile is laid, water can still get under if you have a flood (again). Grout is porous. Depending on the amount of water, how dense the thin set was laid, etc... you can have efflorescence or tile lifting due to water damage. If you go this route, by extra material for potential repairs and keep some grout in a sealed plastic bag.
As an alternative, there are amazing floors out there made of virgin vinyl. They are known as LPV. It is a waterproof, click lock floating floor. They are rated for installation on grade and approved for wet areas. Lifeproof (sold by The Home Depot for about $3.00 a sq ft.) has a treatment on most of the flooring called UltraFresh. It is a mildewcide that is impregnated on the top and bottom of the plank. Life proof has a PVC core, so there is not swelling or potential damage. Pretty cool stuff. Do not confuse this with Pergo or other knockoff LAMINATE floors. Luxury Plank Vinyl is making that completely obsolete.
I wish you a dry, healthy and Merry Christmas.