Hello, I am picking up the used 125 gallon tank with sump that was used for saltwater fish and hasn't been used in a while. It is for my 2 11" Oscars and 13" Plecos. Is there anything I should be concerned about? The guy selling it to me said he was going to clean it real good (he has been in hobby for over 20 years) and is delivering to my house as well as setting it up. I am going to try to convince him to transfer my fish. He of course said we had to use the same water that is in my current 75 gallon tank. Any advice? Thank you all!

Yes, you can use the same tank filtration/lighting in both freshwater and marine. If you get some details about this tank we can give you some advice.

what would you like to know? so far from what I learned today, it is 72 x 24 125 gallon. with sump which has a 40 gallon tank below in cabinet with the pipes that are hidden in a black box that is in the right corner of the tank. sorry, am guessing what you are wanting and it probably sounds foolish what i am providing. he showed me the crate looking pieces below with a thick black sponge. don't know what else to add. i posted a pic on my page.

I say congratz on the new tank.
Your fish will love it!
Did the seller provide you with any filtermedia to go into the sump?
I use different sorts of porous stone, ceramic rings and foam slabs in mine.
Just provide the beneficial bacteria with a lot of surface to bind on.


Did you see how the piping and filter were attached before you got it?
I sure hope so, or i hope you like puzzles!
Anyways, it's gonna be so much fun to get it up and running.

edit:uhm, i missed something, the tank is setup and running allready???
lol, it's been a long day...........
and here I am , giving answers to questions you didn't even ask.

The seller is setting the entire thing up for me. Thanks.

once it is set up, you can transfer everything from the smaller tank to the
bigger one, add same amount of water for gradual adaptation...

please keep us posted

I bought a 135gl that was a saltwater reef tank, and used it for freshwater. I vacuumed the tank out really good, and then scrubbed the hell out of it with a sponge and a scrubbie; then rinsed it all out with nice clean water. I filled it up and cycled it for a couple of weeks with the filter from the old tank. Then afterwards I took the water out of the old tank, and dumped every last possible drop I could into the 135, filled up the rest with fresh water. Never had an issue until it sprang a leak. LOL

thanks. so how do you fix a leak?

can i do this immediately or do i have to wait a few weeks like person below did with theirs?

if you put old filters in new tank, what were you using in the old tank with the fish still in it? thanks.

Fixing a leak is a whole other thread. LOL

Yes you should cycle your tank before putting fish in. I used a couple of HOB filters I had lying around the house on the old tank. Which was a bad idea at first because I didn't let them colonize properly which put my tank into a cycle and I lost a very large Lace Cat because of it. (Brain dead moment.) Lesson learned - colonize new filters first, before removing already established ones. lol

okay, i think this is my last question. so, i can just let the sump go for a while by itself? maybe not my last question.... the filters i have now in the old tank need the water level to be pretty high to function, how am i going then take water from this old tank to put in new one? am i up for a large challenge here?