I think that if you don't have a nutrient problem the main reason for wc is to replenish trace elements, however, they can be dosed.
I am pro wc but that doesn't mean it's necessary.

you had cyano!.....that means excess nutrients!.....

Maybe I'm confused. I thought clams take in neutrients to grow.

And why would excess neutrients effect one clam negatively but not the others?
Some of my corals seem to have benefited in the last month while I've had cyano

Clams like nitrates. True.

My last battle with cyano was due to a Cbb which I was purposely over feeding my tank so it would eat. Even though I tested water and got zeros across the board I new there were nutrients in there that were feeding the cyano. I wonder if it was leach from the rocks as a few months before I had a ha outbreak from high po4. Even though the water colomn did not test high in those nutrients the rock and sand could be rich

Thanks.

If all fails I'll just do a fowlr and get the clown trigger I've always wanted

I think there is more to the equation than that.

yeah, a large 8" clown trigger, a big harlequin tusk, couple of angels, a sohal tang, couple of lookdowns, would look awesome in a 180

and don't forget to quarantine everything, as it would be sad to see that bunch of fish die in less then 2 days.

Actually, not at all. I have NEVER had P04 or N03 readings n my tank - I mean NEVER! Not since day one of the tank. I have incredible flow, new bulbs, I under feed my tank, exceptional filtration, there is NO way I should have cyano, yet, it grows in the darkest parts of my tank, on powerheads and in front of the returns of my closed loop. Cyano is a bacteria, not an algae. There are so many different forms and it's next to impossible to know what is feeding it sometimes.

Of course, you need to be sure you do not have excess nutrients. Agreed. But I got Cyano after trying bio pellets and I can't get rid of it, despite trying everything that has been suggested. Even Red Slime Remover. Something is feeding it. Just can't figure out what. The funny thing is, my tank, otherwise is all but perfect. Corals are happy, fish are happy, parameters are spot on and it only grows on the rocks, never the sand. Go figure.

Getting Cyano after bio pellets is very common if you don't start gradually and you don't use MB7. The latter is very important to establish beneficial bacteria before starting bio pellets. The beneficial bacteria will out compete the Cyano when consuming the bio pellets or other carbon sources (like vodka).

But have to ask, if you have zero N03 and P04 why are you even using bio pellets?