I used chemiclean red slime remover to great effect prior to the sand change. 
If you saw it now you’d think it was a different tank. With all hours I’m putting in at work I’ve been slacking , gha is everywhere but corals looks better than ever
These are green scat. They are a brackish fish, omnivorous, but they peck at the algae continuously like tangs. Very useful, and they sometimes shoal. They can grow large over time. Some of the front dorsal spikes are toxin producing, but I have never been close to being stuck. Some have alleged they eat aiptasia (why I originally bought them) but I never observed this. They have been great fish for me. Would highly recommend. I think I got the from live aquaria, but was not able to find them there just now.
How is your cowfish doing? We love ours - he has learned how to spit water at the surface when we are by the tank. Bad habit as I have to keep cleaning the front glass but he's adorable.Biggest change is exchanging the black hawaiian sand for some Caribbean crushed coral. Of course that is largely turning green
Ah the ugly phase...
Not worried about the cycle because the 75g tank is plumbed into 300g of mature reef. Just need to get through the uglies.
Added a long spine urchin. Slightly worried about the trigger “El Greco” as he gets bigger.
The wifey picked out a Cowfish. Thinks this lil fish is “the cutest ever.”
And a juvenile Naso
Lastly, a bunch of photosynthetic gorgonia and the aforementioned bicolor goatfish (love his barbells)
“Mogli” the cowfish is doing great. He is still pretty small, but he is willing to compete with the snowflake eel and much larger puffer for food. Seems to be growing well. I look forward to him spitting at us hahaha. It is my wife’s favorite fish - she actually bought and named him. Tons of personality.
Our boxfish name is Junior - he competes with everyone for food and shares the food contraption I had to make for our Nori with our Sailfin Tang - for reference he's about the size of her tail. I tried to include the video I managed to get of him spitting water. It's a bit dark but you can see it.
Unfortunately I had my first ich outbreak about 2 months ago. The naso was not the first fish to get it (that I could tell) but he was the first to pass.
Honestly, with our new aqua-scape we have little sand that is showing and we have a combo of Black Hawaiian and some sort of white - I know it was all livesand from Caribsea when we built the tank. The black is "lighter" than the white and winds up on top. The wavemakers create areas where the black can't sit. We also have a good spread of bottom dwelling corals - Trachy, Lobo and Symphillia and a smattering of zoas and mushrooms. If the goatfish even just mixes the sand up a bit that'll be good in our book. Most of our fish are appearance > function. We tried sand-sifting starfish and it didn't last a week before someone ate it's arms. Our other starfish are fine but something ate the sand sifters arms.
LOVE if hahaha
The goatfish does a bit of sifting, and it is interesting behavior, but I would not say that it results in a meaningful turnover of the sand-bed like cucumbers, sand sifting stars, or gobies. That being said, I have never been able to get sand sifting gobies to work long term either
I think the goatfish gets his points for visual appeal > utility
good luck
Ours isn’t very big at all - maybe the size of a 50 cent piece. We’ve had him less than 6 months and he’s learned to spit.
