Using water from existing aquarium when starting new one

Thinking about starting a small nano tank. Will put some new live sand and some LR in it.

When it comes to filling it up with water, obviously i could use all clean freshly mixed salt RODI.

What if when doing water change on my big aquarium, i used some of that old water for the nano instead. Would that benefit/kickstart the cycle sooner or is that a horrible idea?

Seems like that water could have bacteria/organisms/organics in it that could benefit the new tank and make it cycle faster?

Thanks.

 

i do that all the times when seling/trading tanks, you could just fill the whole thing with waterchange water and wait a couple weeks for a mini cycle and your good to go

 

From what I've read and heard I believe the water won't really help at all. Live rock and sand are wayyy better than the water. Imo I would start with new water.

 

an established tank does have more beneficial bacteria and such on the surfaces in the tank rather than the water, but you can put cycled water in an empty tank and put a fish in it without it dying. ive filled up a 40 gallon tank with water from my 90 50% water change and put coral and fish right in and it didnt even cycle. it couldnt hurt.

 

Water contains few beneficial bacteria. I choose to start out fresh every time to reduce the chance of cross contamination from old to new. I also never take change water from one tank to fill another for the same reason, I like all mys systems to be freestanding so any problems would be unique to that system alone.

 

Well, you could go either way, with pros/cons each way.

Using new water will prevent cross-contamination, but will require you to use all new and seperate stuff. Anything that touches one tank should not touch the other, otherwise the purpose is defeated.

Using the other tanks water will introduce whatever you have in that system, but you can share equipment, and whenever you do a water change, just use the water from the big system as the "new" water for the nano, as long as it's parameters aren't way out of wack.

My point is for you to understand that the implications of your decision go way beyond the simple question you asked.

 

a nano aquarium should be fine. larger tanks you may want to test for a few days