Question About Moving Fish To A New Tank

[CrystallinEntity]

I have a question about moving some fish into a new tank.

My husband and I got a 10gal aquarium a few months ago. Our intrepid scout fish was a dalmation molly. It turned out to be a pregnant female, and we got 6 babies. (Unfortunately, mama fish died shortly after; it appeared to be fin rot.) Since 6 full-grown mollies is a lot for a 10gal, and since we want more fish someday anyway, we have recently set up a 55gal tank.

In order to reduce the cycle time in the new tank, we put in an old filter from the old tank. We also decided to only move 3 of the 6 mollies at first, to reduce the load while the new tank gets established. We do eventually want all 6 in the new tank, but we were concerned that if we did something wrong, we'd lose ALL our fish, so we wanted to be extra cautious.

We made "the move" yesterday. We treated it like getting new fish from the pet store: we bagged 3 of the 6 fish (separately), put the bags in the new tank, and slowly added new tank water to the bags to acclimate them, before releasing them. This was overly cautious, since the water in both tanks is the same (tap water only treated for chlorine), but we are new to this.

Now, it has been almost a full day since we moved 3 of the 6 fish. The fish left behind in the old tank are acting more stressed than the fish we moved into the new tank. The new-tank fish are swimming at all levels, are being active, etc., while the old-tank fish are hovering above the gravel and hiding behind the decorations. (Before the move, all 6 fish were very active.) Also, one of the old-tank fish has a huge dorsal fin which he (?) used to fan up and down, but now it is completely up all the time. We think they are reacting to a sudden drop in their numbers. (I would be upset if a giant bag descended from the ceiling and scooped away my friends. ) They were born in the 10gal tank and have not experienced anything like this before. It has always been the 6 of them.

So, my question is: should we go ahead and move the final 3 fish to the new tank now (rather than waiting to confirm the new tank is cycled), so the group can be together again? We don't want to overload the new tank, but we also don't want the old-tank fish to be stressed. They have been acting this way since last night, when we took out the third fish, and so far today, they don't seem much better. They still come out of hiding to eat, but they are not nearly as active and perky as they were before we took out 3 fish.

Thanks!

ps. Here are the tanks' stats:
Old tank (10 gal): ammonia 0, nitrite 0, nitrate 10-20 ppm, pH 7.2, hardness 150-300 ppm (it's hard to tell exactly), alkalinity around 120-180 ppm.
New tank (55 gal): same as 10gal, but nitrate is 0. The alkalinity might be a little less (120).

 

[2excitedkids]

Hello,
I think, though am fairly new to all this, that if you move the rest of your mature filter from your old tank with the remaining fish then the tank should be immediatley cycled. This is because the majority of the bacteria numbers needed are on the filters.
I do not know what percentage of bacteria live in the substrate etc though.

 

[Scotty001]

i would move the rest of your filter media from your old tank and into the new tank and also move the other 3 fish into the larger tank, you wont overload the filter as they have all been in the smaller tank with the old filter media which is already used to coping with the demand they produce.

you would only overload it if you decided to put another 4+ fish in with the mollies, do remember tho if you have a mix of male and female mollies they are going to keep re producing !! on average a female gives birth to 30 - 40 at a time ( as i found out myself the other day) and have been known (but is v rare) to get to numbers of 150.

you have done the right thing being cautious moving the fish and re acclimatising them, i would say you couldn't be too cautious doing this myself. The main thing to look out for is to keep the water temp the same in both of the tanks.

 

[CrystallinEntity]

Thanks for the replies! The mollies we left in the small tank seem less stressed now -- they are more active and aren't hiding as much -- but since it is safe to move them to the new tank (since we moved the old tank's filter), we will go ahead and move them soon. They will be much happier in the larger tank.

Another motivation we had for keeping some fish behind in the old tank was to keep the old tank cycled, so we could use it as a quarantine tank. Our idea was that we would move the remaining 3 mollies into the larger tank the day before getting new fish, which would leave the old tank cycled. But, I realized later that we could just do the filter shuffle. I've found some informative posts here about setting up a QT tank.

We think, based on the shape of the anal fins, that we have 2 females and 4 males. I suppose we could keep the 2 females in the small tank, but then we'd have to get another tank for a quarantine tank. Of course, if the fish inbreed, that certainly won't be healthy in the long run. (There's soooo much to think about!) But I digress.

 

[OldMan47]

Entity, you are doing fine with the fish where they are. After you have run the old filter and the new one both on the new tank for a few weks, the old filter will not be the only thing supporting your cycle. At that time, if you want to expand the molly numbers, I would advise to get the ratio up to 2 females for each male before increasing the number of males again. With TDS of 150 ppm or so you have just enough hardness in the water for mollies. If anything, they would probably do well with more but are OK as is.

 

[2excitedkids]

Day2 after change to new tank with old filter media- faintest hint of green on api ammonia test (even checked tap water to be sure). Nitrite 0.

Did 10 percent 40l water change, fingers crossed that does not go any higher.

One albino cory did not survive the day of change sadly ...not had much like with corys sadly! Rest all seem ok,fed today and all hungry.