High Fiber fish foods?

[Schulks]

I think my yellow watchman goby is constipated because his belly is large/pale looking. I saw him pass a large one the other day too lol. It was solid brown though.
I also realized all my food is high protein/low fiber.

He recently started catching a few pieces of seaweed from the flow but I just started feeding that.

What foods can I toss in to get him some relief??

I've read about boiling and peeling some peas but I'd like a fish food I can just buy and toss in.

 

[Cthulukelele]

Watchman gobies will often eat until incredibly bloated and take pretty big poops, but if you're concerned I know some people will use Epsom salts or raw pea as a laxative. Live brine is also a decent laxative