I've used bleach as well in our 120g before restocking it.
The process we did:
- removed all livestock
- scraped off all the coralline algae from the sides and bottom (BB tank), siphoned out all the coralline and detritus and removed all saltwater
- filled the tank with untreated tapwater, scraped any areas of coralline missed during the first scraping, put in the original powerheads and heaters
- added about 1.5g of bleach, turned on powerheads (but did not turn on heaters) and let them run for 3-4 days
- drain bleach water from tank, making sure to siphon out all particulate matter
- filled up tank again with tapwater, tossed in an overload of dechlorinator (maybe 5 oz) to make sure all the bleach was neutralized and let the powerheads run another 1-2 days
- drained tank again, making sure to siphon out all particulate matter
- soaked and cleaned powerheads and heaters in vinegar to remove all coralline, sponges, etc. before using in the tank again
- began adding pre-made saltwater to tank as well as water from the tanks our livestock had been in, and set up the 120g again
HTH
