I have a question on building racks for my ball python collection. Do you pretty much just build shelves where the rubermaids will fit in so there is no space for the snake to get out? Do you have any other precaution so the snake can't push themself through?
I'm not sure exactly what you mean by "no space", but that's pretty much it. My only precaution is to not build your racks with too tight of a gap, which seems to be the common mistake for first-time rack builders. It is always easier to shim too loose of a gap then it is to increase too tight of a gap.
It may seem to make sense to build tight but the problem is that boxes warp slightly from the heat and racks can sag ever so slightly which can make boxes slide poorly over time.
If I were building a rack for juvenile or adult BP's I would probably shoot for about 3/16" gap. In other words, if the boxes were exactly 6" tall then the space between shelves would be 6 & 3/16" tall.
For hatchling BP's probably about 1/8" gap.
How many ventilation holes you drill depends on many factors. But in most cases the gap around the top of a box in a properly built rack offers a lot of ventilation. If you add holes to the box they should be down low so heavier-than-air gasses can escape and spilled water can evaporate more quickly.
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Currently keeping:
6.10 Gonyosoma oxycephala (Javan, mixed colors)
1.1 Philodryas baroni
1.0 Rhodesian Ridgeback