Snails at surface, one died?

[Isosceles]

I just want to be sure, I just redid my reef and scrubbed the sides, so I'd understand if the only reason they're up there is for the algae I missed. They aren't stationary, they move around, and some are still on the rocks but the thing that's concerning me is that two of them fell off the glass last night and one (chestnut turbo) died. I don't know if anything made them fall off, and I'm assuming the one that died just got eaten by the hermits while trying to right itself, but the fish (clowns) are also kinda hanging out in the top corner a bit, not swimming against the flow with their fins clamped or gasping at the surface but they're just kinda up there. Not tight in the corner like they're "hosting" the corner but just swimming around under the HOB. They come out and swim around occasionally. The cardinal has a full belly from a night of eating pods so I know the biodiversity of microfauna in my tank is still good. The coral I was trying to save by redoing the reef is actually recovering and opening more too so this makes me less inclined to believe it's a water quality thing.

Temp: 78.1F
Spec. grav.: 1.025
pH: 8.3
Alk: 8.3 dKH
Mag: 1470
NO3: ~5ppm

I've heard of turbos not doing as good in typical reef tanks because of the fact that they're coldwater species (margaritas/mexican turbos) but chestnut turbos are from the Caribbean so I'd expect them to at least tolerate the warmer water better. I doubt it's that and I hadn't had the one that died for that long.

Any ideas other than "they're up there for the algae I missed when cleaning the tank, two happened to fall off and the hermits got one of them while it was upside down"?

 

[Mr. Mojo Rising]

The oxygen content is higher at the top. Is the water surface agitated by a powerhead? Do you have any water movement besides the hob filter? There should be ripples going across the surface and its good to see little air bubbles enter the water.

 

[Isosceles]

The oxygen content is higher at the top. Is the water surface agitated by a powerhead? Do you have any water movement besides the hob filter? There should be ripples going across the surface and its good to see little air bubbles enter the water.

Yes, I have the hugger bootleg gyre on sine wave at 90%

 

[Mr. Mojo Rising]

Then I don't know, sorry. But if you can attach a short video the fish doctors might be able to help you out. #fishmedics

 

[Jay Hemdal]

Yes, I have the hugger bootleg gyre on sine wave at 90%

Multiple snails dropping off and dying at the same time is worrisome. Losing a snail here and there over weeks/months is normal, but seeing them drop like that isn't right.

Bulk water flow like these units produce isn't always good for proper gas exchange - you need to ensure the surface water tension is being broken - I like to use air stones, but I understand that people avoid those for aesthetic reasons.