Is a high kH harmful to fish or crabs?

[tilla]

I have a kH of about 16 with a ph of 8.3

Is that too high for kH?

I added 4 hermits to begin controlling the brown stuff and 3 dies over night... Tank is about 3 mos. old and fully cycled with about 60 lbs of LR...

Also, Even keeping the lights on for a short amount of time, 4 hours, causes quite a buildup of the brown stuff. Any suggestions as to what could be causing that? I have used only RO/DI since the start.

Thanks,

[tendar]

Your alkalinty is definetly to high if your readings are correct. Dont know if would be enough to kill hermits though.
The diatom algea is just part of normal system establishment. Get some snails to help control it. Genreally denpending on what snails your get 1-2 per 5 gallons of water. The diatoms will burn them selves out in a few weeks once you start leaving your lights on.
Have you dont any water changes since starting the sytem?

[tilla]

I have done about 10% every 3 weeks. This is of my own doing... When LR was first introduced, ph dropped fairly quickly. As a result, I overcompensated with my additions of buffer...

What about for fish? Do you know if those levels would be harmful to fish? There are none in that tank right now, but within the next couple of weeks, I would like to re-populate...