Wish I could share some coralline with you if it would help... I have sheets of it coming off my back glass. In fact, I need to scrape some of it off about every two years. It just starts to peel away.
For me, I wish I would have changed the overall from a more standard peninsula style (i.e., large box that goes all the way to the bottom) to a ghost-style. It would have meant patching and drilling which I didn't want to deal with but I think it would have been worth it.
My recommendation is to keep going, and NOT start over. I went through some pretty long ordeals with my system and in a couple cases, it took about a year to turn back around. Such a slow process but that is the only way to make sure that you are heading toward a stable system. Fast changes will just lead to cycling back and forth between two sub-optimal states.
Adding a refugium will certainly help so that would be my first suggestion. I would also suggest checking out an oxydator. This is pretty cool "tech" that will help to increase oxygenation and water clarity, etc. I have one in my 300DD (size W) and it seems to have made a difference over the years. Not too common in the US but can be found.
The ICP will be helpful and you'll want to probably do it once every month or two (especially with Moonshiners... I do that too). This really helped me to get everything under control as it removes most of the guesswork.
Good luck!