Partial water changes from established tank

[Nandez13]

I'm running two tanks at the moment. A nano tank that's been going on for about a year. It has coraline algae all over the rock, glass, heater and am able to keep SPS in the tank.

I also have a 75 gallon tank that's been cycled for a little over a month. I was wondering if there are advantages of using water from my established nano tank to do partial water changes in the new 75G. I typically do a 10G water change on my 75 so what I do is: mix 10 gallons of saltwater; remove 5G from my nano and add to the 75; add 5G of new saltwater mix to my nano and the other 5G of new saltwater mix to my 75.

I believe the nitrifying bacteria live on the rock and sand so I'm not sure what the pros/cons would be of using water from an established tank. I've done this so far for the few water changes that I've done since people seem to do similar when starting a new tank. I did use some live rock and sand from the established tank to seed the 75 and then redid my nano aquascape.

I'd appreciate any input.

 

[KathyC]

There is very little bacteria in the water, better to give the 75 freshly made SW during it's changes. It will build up bacteria to the level it needs to become balanced as long as you don't stock it too quickly.

 

[Nandez13]

There is very little bacteria in the water, better to give the 75 freshly made SW.

Yea kinda figured, thanks

 

[Dan_P]

Interesting question.

My first thought was a "con": you could be seeding the new tank with disease organisms from the old tank. On the hand, you could just as well be seeding the new aquarium with a lot of different beneficial organisms, not just bacteria. The key point is that you would be seeding organisms not introducing enough to speed up the cycling process.

I suppose one could argue that there might be a benefit at the start of a cycling process, but since you seeded the new aquarium with live rock from the old aquarium, any initial benefits of adding old tank water to a new aquarium may not exist.

So, after going around and around on this, there does not seem to be much harm or benefit with your water change regime.

It will be interesting to hear from a few more aquarists. I can see Kathy C's point.

 

[Nandez13]

Yea, figured I'd throw it out there for people that run multiple tanks.

Giving it more thought I realized I don't test the parameters in my nano right before doing a water change. I don't expect the temp, SG or pH to swing as they're generally consistent but I would expect my Ca/Alk levels to drop a bit once the tank is ready for a WC. I don't dose my nano tank where I keep SPS, I just do regular water changes to maintain its levels since I know my calcium will be depleted a bit.

I guess it can be helpful in the initial stages of a new tank but once it's cycled and running it may not be doing much.

Wouldn't mind hearing from others though

 

[lnevo]

I'd say the best pro is saving on salt. Depending on the bioload though you might be giving depleted SW to the next tank. I might suggest going from new tank to old instead.

 

[andylee]

The downside is that you are only changing 5 gallons of water in the nano tank, so you aren't getting the full benefits of the water change (removing nitrates, replenishing trace minerals, etc.).