No flak from me is intended and if you came to a keeping method that works for you and frog, it's cool

. Personally see your method as heavily dependent in daily handling and on frog pooping after feeding (some won't). Also, the wet substrate could harbor molds and bacteria.
When it comes to Pixies as pets; prefer and recommend a large enough enclosure that can be set as either a 2/3 wet-1/3 dry or 3/4 wet-1/4 dry. The wet section having as large as possible canister filter (10X the rated volume is good start point) as can be afforded and an accessible platform made of flat stones or similar connecting to the dry area. This area will have shredded coco over a layer of clay balls (to keep coco dry above the water table) with a layer of landscape fabric between them).
Targeted maintenance is weekly water changes of 25-50% (affected by frog size, water volume, and filter efficiency) to keep Nitrates below 20-25 ppm. Filter media is to be cleaned during WC with tank water. Dry area get's spot cleaning (normally unneeded) and monthly changes. Good luck

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