fishless cycle?

[i like fish]

so i put these shrimp in to cycle my tank and they are all gone now, but now there is a blakc residuey stuff all over my sand and such, what is that??? any help is good

[lando]

Could be an algea bloom. Is your tank cycled yet? What are your water parameters? If all is well, I would syphin the stuff out and do a water change.