I will see if I can get them to spawn on a flower pot bottom like Nicole uses.
Mine took right to it. One look and the male went, "Hey, honey, LOOK!" They love it and are very protective of it, even when their are no eggs. I don't think you will have a problem getting them to spawn on it. An unglazed tile will probably be just as attractive to them.
They don't have any eggs right now and the scooter is always VERY interested in their pot when there are no eggs, but she doesn't bother their nests -- I think the copepods come out to eat the residue after the eggs hatch. This afternoon it was very cute to see my male trying to move her off the pot without being aggressive to her. (They have no such inhibitions about chasing the other fish, but the clowns like her for some reason.) Papa clown was pushing his nose UNDER her and trying to lever her off the pot.
The scooter, as usual, ignored everything and did whatever she wanted to do anyway. Ah, the Zen of Scooter.
Drill the tanks. I'd also invest in a decent sized air pump on a backup battery, and you can easily run a DIY air manifold along the PVC, too. I use 1/2" irrigation hose and 1/4" irrigation connectors, attached to air valves and thence to rigid tubing. Easy and cheap.
For that many tanks, a Luft air pump will do nicely as emergency backup.