Am sure silk plants would be suitable*I would recommend live plants many reasons" firstly they will help biologic balance are excellent for competing with dreaded algae * if you add in LONG stalk versions of https://m.ebay.co.uk/itm/XL-Anubias-...cAAOSw3utY7T1z these are ideal ANUBIAS are very hardy do not require planting just fix to object preferably drift wood which is my next bit of advice * drift wood pre boiling soaked source from pet shop* no sharp edges* is ideal and gives a very natural look to tank especially with the ANUBIAS atached' the plants help fill the open void to the top and the frogs will love nothing better than basking on there sturdy leaves # if your lucky source solid piece wood shaped like a bridge where the frogs go for there quit time# its not enclosed i can still see right through which i believe is important as if you give them total enclosure u will see much less of them