I decided not to patch that tank corner, after being reminded it's quite likely to fail (even if I get it to hold water, could fail at later point from weakened structure) and that would cost me a lot more in damages and maybe dead fish than just buying another ten-gallon tank and avoiding the risk.
Did you notice the ugly white crap on the heater suction cups in my tenner, and that it was detached from the tank wall? Failed to stick. I kept putting it back on, finding it loose again. So I removed the suction pieces, scrubbed off the white crap with an old toothbrush, dropped the parts in very hot water (boiled, then taken off heat source) for a few minutes. This softens up the rubber and then the suction cups hold again. I've done it with the ones for my thermometers before and it worked this time, too.
I realized I really don't need to target feed my kuhli loaches. I've seen them kicking up fine particles from under the driftwood log and wondered about that. Then the other day when moving some plants, I saw the kuhlis scurry over where I had disturbing substrate and there was a little depression. They darted in and started sifting the fine mulm through their gills. I've seen video clips of peoples' kuhlis doing this with sand- they filter out edible particles through the gills- but never thought mine would do so because I don't have sand. Should I feel bad there's enough mulm on the bottom they can sift it like this in places, or glad there's natural food accumulating from biofilm and microorganisms. (Interesting article about bacteria and microorganisms in the aquarium here).
I probably will occasionally still put a shrimp pellet under the rock for them, just because it's so hilarious to watch them all cram in there after it, haha.