Please note: As we do not have the necessary information to determine how land hermit crabs are affected by ammonia build up in the water and to what degree we err on the side of caution and treat our water as we would for fish. All information regarding Prime is based on the assumption it is being used in a stable fish tank. Our use is much different. Our primary reason for using Prime is to remove Chlorine and Chloramines and heavy metals from the water and Prime does that well with no recurrence that requires retreatment.
Ammonia build up is only an issue when using semi permanent deep water pools.
You can refer to this link for more information (specifically the comments made by the Seachem staff):
http://www.seachem.com/support/forums/forum/general-discussion/2431-questions-about-prime
This link is now gone so here is a screenshot of the comment from Seachem Staff
It’s almost impossible to overdose Prime:
Who does this affect:
Anyone who premixes water with Prime and stores it for later use
Who this does not affect:
Anyone who treats with Prime at the time of a water change
How do I correctly use Prime:
Standing water dishes/pools:
- Change the water entirely every two days. Treat with Prime right in the dish or pool if you wish, swish gently to mix.
Bubbler enhanced dishes/pools:
- Change the water entirely twice a week. Add Prime when adding new water.
Filtered semi permanent pools:
- Partial water changes every two weeks and retreat the pool. Change ¼ of the water.
- Top off the pools as needed and retreat (unless you have a proper ammonia test kit).
- Don’t scrub your filters and parts squeaky clean, keep the good bio stuff.
- Do rinse everything off with Prime treated water.
To correctly test your water for ammonia build up you will need a good quality test kits. Cheaper kits will not work with Prime and will always read toxic.
Seachem Ammonia Alert: http://amzn.to/2EjmfcX