no its no harm
drain tank catch clean water for re use
take out rocks take out fish
clean tank out
add in sand that you pre rinsed in tap water for 2 hours until its laser clear. final rinse ro, use this step no matter what sand you use and dont skip this step no matter what sand you use. refill/add back its skip cycle. do NOT buy bottle bac for this job you are cycled and changing sand does not uncycle.
you might consider altering this step, don't. run the pre rinse exactly as listed-any sand you buy, run it.
it is very important to balanced reefing that we dont attach buying bottle bac with every access job, these are not doubted mechanisms at play, we do sandbed swaps by the hundreds in threads.
Bottle bac sellers depend on forum peers to be scared of losing bac, and sell each other on buying more. Show us how it can be done free of buying new bac, it keeps balance in the game.
Your rocks keep all the bacteria the system needs. even if you didnt put sand back in at all it wouldnt harm, we do this in our sand rinse thread to change to bare bottom. we do it all at once, with no bottle bac on the reset.
The only reason people doubt this mechanism and buy bottle bac anyway, just to have insurance, is due to completely false cycle training using rules written by bottle bac sellers. They are held to account here.
If you are reading this thread to cure a tank invasion from a link I sent you, we do not need to identify your type of invasion here we do not need you to test anything at anytime regarding nitrate, phosphate etc Above all, we do not need to see a microscope slide picture of your invasion at...
www.reef2reef.com
thats fifty pages of tap rinsing on tanks ranging up to $20K sps tanks done all at once. Bottle bac is not used, notice the trending