Hermit Crabs
High humidity, deep substrate.
Go with the Straightforward Choice for a simple cleanup crew or the Advanced Ecosystem suggestions to take your bioactive ecosystem to the next level!
Straightforward Choice: Springtails
Pseudosinella violenta (Bylas Ant Springtails) - The best cleanup crew springtail for most scenarios. Very fast breeding and surface active cleaners.
Advanced Ecosystem: Springtails
Maximize biodiversity: Mix Entomobrya assuta var nov, Lepidocyrtus sp, Proisotoma minuta, etc. See the full species information list for picking additional springtails and to learn which environmental niche each species specializes in.
Straightforward Choice: Isopods
Porcellionides pruinosus (Powder Blues or another morph) - Active, fast-breeding, and effective isopods.
Advanced Ecosystem: Isopods
Maximize biodiversity: Porcellio scaber, Cubaris murina, Cylisticus convexus, etc. See the full species information list for picking additional isopods and to learn which environmental niche each species specializes in.
Quantity
Quantity of springtails and isopods required for a bioactive enclosures varies based on enclosure size and the amount of time the enclosure is establishing before adding the main inhabitants. As few as 50-100 springtails and 5-10 isopods per species could seed a 20 gallon enclosure if it is set up in advance and the cleanup crew is given fish food once or twice a week to help them grow in population. For the 20 gallon example I recommend 300-500 springtails and 30+ isopods if they are needed immediately. You can get away with starting with fewer isopods or springtails in the environment and still have the main inhabitants, but it will take a while for the CuC to start performing their duties effectively.
Crucial Information
Avoid the isopod species Porcellio laevis as they are very protein hungry and may harm molting crabs.
Additional Information
Always provide a thick layer of leaf litter for the cleanup crew to hide in and graze on. For a naturalistic look, I recommend adding crushed maple leaves on the floor with live oak and magnolia leaves on top. Fallen leaves make up a large part of the isopod diet and soft leaves like maple are their preference. Springtails will also graze on the maple leaves as they decay.