Nonsense. There's nothing in tank water that will prevent a cycle. If you add fish to an empty tank with nothing but tank water, ammonia will rise. The only difference between clean fresh salt water and tank water is one is clean and fresh, the other has fish poop in it. The "bacteria" in DT water is insignificant.

I was told different by a local reefer loooong time ago and just followed this practice of using old tank water to start a new tank. I do agree there can be a spike but less significant than if you use fresh mix with no bacteria whatsoever.

When I transferred everything from my 90 to my 180 I did a process I will call transfusion I actually pumped back and forth from one tank to another for a week before transfering Rock coral and fish over. I had no spike whatsoever in the swap

Ya, I hear this all the time, but it's not true. Water contains so little bacteria that you wouldn't notice old from new in any kind of new tank, QT or otherwise.

If you did this thing above, and then transferred rock over, then that is where your bacteria came from. I transferred my 90 into my 180 with all new water, no spike or anything else either :) The bacteria is on/in the rock.

So with this would it then not be advised to have live rock or dry rock to become live in your qt tank not only for fish Hiding but for a stable qt system. Otherwise your struggling with what ever ails the fish as well as keeping parameters in check. It may seem a waste of live rock. But in my mind the best way to run a qt tank

+1

By using water from my DT, just figured I would kill two birds with one stone so-to-speak (I like birds LOL) ...my DT then benefits by getting a bit of freshly mixed water.

I keep my DT clean and my levels are all good in regards to nitrates/phosphates etc.

The fresh water gives a tiny boost to the calcium and alkalinity and magnesium... and with all my sps every tiny bit helps LOL

The QT tank does not need this as of course there are no corals in there. That's why I take the water from my DT.

The water does not hold the bacteria.

Come to think of it, initially I changed close to 50% maybe every other day... then gradually eased to 25% twice a week... then weekly.

But remember, I did put a small piece of liverock over from my sump, which does harbour bacteria.

Maybe someone can give you a piece.

Just don't put anything back into the DT from the QT (except the fish :mrgreen: )

In my case my qt tank will also double as a frag tank. Not to be used as a hospital tank that some use to dose meds like copper. I don't plan on using copper ever but if need be I can set up a hospital tank for this purpose.

I currently have rock in mine, but normally I keep a fully cycled aquaclear foam block in my main sump for quick QT setup. This way, I can have a tank fully cycled in an hour

lol I have 3 foam blocks in my sump but never thought to use them in that way

Instant filter :)

I use mine under pumps to stop vibration