That could have multiple causes.
Correlation is not causation.
Which lights, was the par the same ect ect..
No need to really answer.
If the par was different you could have either under driven or over driven the corals thus favoring algae
Your new lights were a change beneficial to a new balance leading to stability.
Just guessing
Stuff like that happens in fw all the time.
Just use t5....
See that CAN be made w/ LEDs. That it isn't has nothing to do w LEDs per se, just implementation..
Easy enough to build.
Here is THE main issue though no factory built led diodes
with the "correct" phosphors ..but 1
norway.kyocera.com
Can't vouch for shadows but mh's s also shadow some.
I hear Phillips would cover all but cost.