Looking to add some fulness and extra fiber to a bit of a hard keeper.

I like adding a 1/2 scoop ofbeet pulp and a scoop of alfalfa cubes presoaked the night before and mix it in their grain. I also add renew gold and two pumps of veggie oil into their morning g and evening meals. 

Alfalfa Cubes 

Ditto. You might even want to try the Alfalfa Cube/beet pulp combo.

Yep, I really like adding the Alfalfa cubes, been doing it for years and the horses and donkeys really love them too, lol. I am adding the beet pulp to the old donkey and my sr gelding's feed but them like the cubes better I have noticed.

Alfalfa or rice bran. Anything but beet pulp. That stuff causes choke.

I have fed beet pulp for many years.   Added rice bran a couple of years back.  Best pulp is just for winter with the herd I have now.  When Dan was alive, he got it year round and it was a lifesaver for him.  

I feed timothy/alfalfa pellets for some extra protein/fiber. 

Not if you soak it like you're supposed to, unless your horse takes massive bites and doesn't chew right. In which case its the animal's issue, not the feed product. 

I have a garbage can that I mix 2 bags of alfalfa pellets to 1 bag of beet pulp pellets. My horses get 1/2 of a 3qt scoop 2x a day, soaked in water. Warm water will make it puff out completetly soft in 5 minutes, so you're not spending forever soaking. I just splash a shot of cold water in after its done to cool it off. In the winter i do add rice bran for my 27 year old who can be a hard keeper sometimes, due to the cushings. He yo-yo's with his weight a lot but I rarely have to adjsut his feed other than adding a cup of rice bran when he starts dropping. I prefer alfalfa over the beet pulp, but when I switched to grain free I added the beet pulp for some extra calories to help offset the loss of the grain I was feeding. But I don't feed any hay pellets or cubes without soaking first to soften. Also soaking is nice because they're getting extra hydration in their system and keeps your impaction risk much lower 

I would feed alfalfa pellets or cubes whichever you choose. I just wet mine, add my supplements and i've never had a problem. Add some oil like flax. or ground flax with rice bran. or try platinum but that might change your whole program. I had my old gelding on it and he got pretty fiery and FAT. So I stopped feeding it lol

I won't feed beet pulp. I tried different brands and everytime I'd feed it the water would be brown almost black. I don't know if that was just from the beet color itself or what but my horses looked like crap on it and one got worse. So no more for me. 

The dark water is some dirt, some natural color from the shreds, & the rest of the sugar coming off. its entirely normal.   Most people drain the water and feed the soaked pulp. Beet pulp is used to add extra calories, but has no nutritional value beyond calories. So they're not going to get any vital nutrients from it. In that aspect alfalfa is better, but the beet pulp is better for hind gut function. They both do much different things for the horse and serve their purpose for specific needs. With my cushings guy its one of my only safe options for feeding, but I give all of mine Exceed 6 -Way so even with it being devopid of nutrition they're still getting their needs met between the alfalfa and the MVP. I don't recommend beet pulp if you need more nutrition for your horse vs just adding basic extra calories. There's a time & place for beet pulp, but its not for everyone