Hi dogstarheaven, and a belated welcome to WAB
(sorry, I missed your earlier posts)
A very commendable effort there. I've always felt that those boxes had potential, just never had the chance to try one out.
A few thoughts though:
1. I doubt if the cats will be much of a threat to tads/froglets while they remain in the water - it's when they emerge on to land that they become most vulnerable. Plenty of plants and a few shelters around the pond will reduce that risk.
2. The box is rather deep, deeper than it needs to be - the greatest biodiversity occurs in shallow water.
May I suggest a modification to your design? Rather than using the bricks to create a ramp for access/egress, use them to build a retaining wall that partitions off about 2/3 of the box, and fill the void created with sand and/or pea shingle to create a gently sloping "beach" effect, extending from above the waterline to, say, 30cm-40cm below. This will create shallow water which you can plant with marginals, increasing the variety of wildlife attracted to the pool, and providing a covered route for froglets to get to land. Wait till next winter to do this though, there's no point in disturbing what you've got this year.
3. If this is in a raised bed, have you made provision for frogs to access the bed from ground level?
4. I presume the box is made of UPVC? If so, you will find that it will ultimately perish from exposure to UV light. Not a problem in the short term (you should get a few years good service), but the material will become brittle and susceptible to damage as time passes. Still, easy enough to replace, I think.
5. Yes, get rid of the "reeds". If it's Greater Reedmace (also known, incorrectly, as "Bulrush") you definitely
don't want it in there, it will take over.
Good luck
T2