Why is he on that diet? Was itprescribed by a vet? Does this vet actually know much aboutrabbit nutrition? This is the equivalent ofa humanliving on nothing but brown rice. It does not provide thenecessary nutrition, even with supplements in the water.Supplements like that are usually not fully absorbed and can't compareto getting itfrom an appropriate food source.
Please start feeding him at least a small amount of pellets.They provide fiber, protein (which he is severely lacking at themoment), and vitamins and minerals. The less pellets youfeed, the more veggies are needed.I know manypeople who feed only a tablespoon or two of pellets to ensure therabbit is getting his vitamins, and then give a large amount ofveggies. For no-pellet diets, I've seen severalrecommendations tofeed a pile of veggies the size of therabbit with at least three, preferably more, types. Theyshould also be getting multiple types of grass hay and maybe a littlealfalfa.
I know you probably meant well, but it takes a lot of work and researchto properly feed a rabbit without pellets. There's lots ofinfo in Bunny 101 if you still want to try. I researched it alot and decided to continue feeding at least some pellets and lots ofveggies. I can't guarantee that I'll be able to give themproper nutrition without any pellets.
I think switching to an appropriate diet would prevent his problemswith water retention and might even improve bladder function.And yes, take the salt water away. Was that his only watersource? Rabbitsshould havefresh water, orslightly flavored if you need to encourage them to drink more.