- Joined
- Jan 17, 2020
- Messages
- 24
- Reaction score
- 20
- What state or country do you live in
- Florida
3.5 gal tank 6 marine hermit crabs. Get salt water & sand from where we got the crabs. Every 2 wks my sand turns black. If i don't change w/I 2 days, crabs die & kids cry. I have to redo the whole tank. What's the problem?




