Bunny needs more fiber-suggestions please

I've had my bun for over 3 years and he has never been a big hay eater. I feel like I've tried everything to get him you eat more hay. It's in his litter boxes, it's in both the living room and bedroom. I've tried all kinds but supply him with 4 different kinds daily. He loves veges and eats a lot of that. I tend to give him larger portions than he should have to make up for the fact that he's not eating hay. He has had a number of episodes of GI stasis over the years but was able to catch it early. His poops have never been large. The last couple days he has had formed and unformed poop. Mushy poop I would call it and stinky. Had to clean up his butt too. Tried papaya and digestive tabs crushed up on greens as he won't ear them hole. Is there something out there like fiber tablets or benefiber that is safe for buns? Can I put benefiber in his water? What suggestions do you have on ways to increase fiber in diet? And yes, he does get some treats daily but I try to be limit. Thanks for your help.

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A rabbit may not eat as much hay if he is able to fill up on pellets, greens and treats. They can be smart enough to try to manipulate their owner. If you try eliminating treats for a time, and cut back on greens and pellets, they typically will eat more hay. That would be an easier option than forcing fiber in other ways. It's just a matter of sticking with it and not caving when they beg for treats.

I have this problem too. I cut out pellets and greens (like grass and herbs), and only fed him hay, and ended up with an underweight bunny which I had to feed up. The solution I found is the Oxbow brand pellets which are made of Timothy hay. Once Pluto was eating these, normal droppings, no more slushy stinky ones, no more need to clean his rear end and he could tolerate greens. We still offer the lots of hay and he eats quite a bit, but it can be hard to get good quality hay here that is consistent in texture, each bale is different and, as we know, bunnies don't like change! The Oxbow Timothy hay pellets are the way to go for fussy buns.