Re: is it a must for clay substrate for pumilio?
It is recommended for Oophaga because froglets often would sometimes randomly drop dead once they reach 4-5 months of age, and that has been linked to Calcium deficiency. If you don't plan on breeding pumilio, or you don't even know you have a pair, it is always good to have clay substrate because sometimes the frogs have other plans. Oophaga froglets can absorb the much needed calcium through their stomach patch via the clay, and then feast on calcium-rich microfauna that have been living in the clay until you find them or they are old enough to pull.
Clay substrate is also good for supporting large colonies of microfauna and providing them a place to stay away from the frogs and keep up a massive population (deep in the substrate), and clay substrate gets the best drainage, so a clay substrate vivarium could last a very, very long time.
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