Same Species, Different Substrate: Raising Juveniles, Keeping Adults

A froglet and an adult of the same species should not be standing on the same substrate. Weight and length are the two numbers that decide which recipe applies this month, and a juvenile putting on 2 mm a month will cross the threshold sooner than the calendar suggests. The difference is not sentimentality about small animals; it is ingestion risk, observation, and the fact that a 15 mm animal loses heat and moisture far faster than a 70 mm one. Keepers who raise a clutch through to adulthood usually end up running two substrate recipes and one transition between them, and the numbers are worth writing down.

Juveniles: shallow, fine, and easy to watch

Start froglets on damp paper towel over a 3 mm gel layer for the first eight to twelve weeks. It holds 80 to 85 percent humidity, it lets you count every insect eaten, and there is nothing to swallow. Move to a real substrate at around three months, 20 to 25 mm deep, with any polymer band below 15 mm and covered by at least 10 mm of medium. Use the finest grade you can that still drains, 0.5 to 1 mm, because a juvenile hunting a 3 mm cricket will take medium with the strike. Fine particles pass more easily than coarse ones if ingested, and more importantly they do not create the loose surface a small frog can pick up by accident. No exposed granules anywhere in a juvenile tank. Humidity for juveniles runs slightly higher than for adults, 80 to 85 percent, because a small body loses water fast; two short mistings and a partly covered lid usually hold that without soaking the floor. Feed on a small tile or a clean leaf rather than straight onto the medium. A froglet that learns to hunt over a bare patch takes far less substrate with its food, and the habit carries into adulthood.

Adults: deeper, coarser, less fuss

Adults get 50 to 75 mm depending on species and burrowing habit, a 2 to 4 mm grade in the band, and 10 to 15 g of dry granules per 10 litres of medium. Coarse granules under a proper litter layer are effectively out of reach, and a deeper bed holds its humidity with fewer mistings: two 45-second cycles a day will hold 75 to 85 percent in a well-vented adult tank. Leaf litter goes on thicker, 20 mm, because an adult’s prey items are larger and drag the surface around more.

The four-to-six-month transition

Change one variable at a time. At four months, deepen the existing substrate from 25 to 40 mm and keep the fine grade. Two weeks later, switch half the floor to the coarser medium. Two weeks after that, complete the change and raise the band dose to the adult rate. Watch feeding through the whole sequence: a juvenile that stops striking, or that strikes and misses repeatedly, is usually dealing with a surface that is too loose or too wet rather than an illness. Growth rate is the other check, and a frog putting on size steadily through the transition is telling you the new substrate is working. If growth stalls, go back one step and hold there for a month. There is no prize for finishing the transition on schedule. Adult tanks settle into a simpler rhythm once the change is done: spot-clean weekly, turn the litter monthly, replace the band every 8 to 12 weeks.

Matching grade to animal size is the whole exercise, and the coarse polymer granules page gives particle size ranges alongside the water volumes they hold at saturation.