First off, that tank is amazing for your first build. XD My White's tank was TERRIBLE when I first brought him home, it took two changes to get to where I am now and I think I need to do ANOTHER rebuild because I'll be adding three more White's in the coming months. XD; But anyway, enough about me...

The screen between the coco fiber and the gravel isn't necessary unless you have live plants in there (or so I assume) and I'm not sure that even if you do have live plants it will be much of a detriment. More people should comment on this specifically because I don't really have the technical expertise to tell you anything, but I wanted to leave my 2 cents just in case.

The moss should be ok as long as you don't see the White's ingesting too much of it. Impaction has always been a big fear of mine, so I am constantly worrying about the moss, but that's just me. I used leaf liter (from Josh's Frogs, sea grape leaves) to put over the moss to ease my mind a bit. It also ends up looking very good in the viv overall.

I have to say I think your pond is a little shallow for White's. Mine LOVE to soak deep in the water at night, I'll see them hunker down and try to get the water over their backs a little. I bought an especially deep water bowl for my first White's, and it may be my best buy for him yet. XD; Is there anyway to make it just a little deeper? 1 or 1 1/2 inches should be good, depending on the size of your frogs. If they're still babies 1/2 an inch should work for a little while. If you want you can get a deeper water bowl to substitute for what the pond lacks, as long as you have enough surface area to support one.

You can feed your frogs in the tank if you want. Lots of people use a cricket bowl, just a glass or plastic dish that is deep enough to keep the crickets from escaping or jumping out. I have to take my big White's out to feed because he has damaged eyes, but as long as their happy and healthy they should do fine if you feed them inside the tank. Besides ingesting the moss, you really have nothing to fear. White's are scrupulous, they'll find the little buggers eventually. XD

Heated water could be good or bad depending on the frog. My big guy used to not be so partial to warm water, but now that he's gotten used to me and the soaks I think he's ok with them. As long as the water doesn't go above the high seventies you should be alright, they might even like it!

Bromeliads are great plants for White's as they have big, thick, strong leaves that can hold up the bulk of these HUGE frogs. Snake plant is also and excellent choice, it's bigger and stronger than the bromeliad and is near impossible to kill. I have both of these plants in my White's viv and the snake plant in my P. tomopterna's viv as well if you want to take a look in my album.

Other than that, all is well, great job! Hope this has helped.