setting up a new fish tank

Question
QUESTION: hi! I have a 55 gallons tank that is cycling right now and planning to upgrade the tank to a 125 gallons tank. Should I wait until the tank is fully cycle before upgrading? or just go ahead and do it? I also have 2 filters in my tank : aqua clear 110 and elheim 2213 running right now so if i wanted to move everything to a larger tank do i need to purchase a new filter? and what do u recommend? I also want to ask how many fish can I keep in the 125 gallons tank? I would love a semi-agreesive tank to an aggressive tank with smaller fish only I mean not like an oscar or a parrot fish but something small. I personally love the sharks so if you can recommend any of them? thank you so much!!!

ANSWER: Hi jane!

If you cycle the 55 gallon tank and then plan to upgrade to a 125 gallon tank you would still need to cycle the 125 too.  It doesn't matter if the 55 is cycled already because the 125 will still need to be cycled also so its up to you.  Keep in mind that if you plan to cycle with fish it would take longer, about 7-8 weeks and cycling without fish (fishless cycling) would take up to 6 weeks.  Both of those filters will be adequate for the 125 tank because they are rated to 175 gallons total.  Are you talking about the bala sharks? They are schooling fish and will need 6 or more per group BUT they get big, probably about 12-14 inches.  There are other sharks that stay small such as red-tail sharks, and rainbow sharks which only get about 6 inches.  Those are ok.  Tiger barbs and tinfoil barbs are small aggressive fish that you might want to also consider since they only get 2 inches max.  But they have a bad case of fin nipping if there are slow moving fish in there.  Gouramis are also semi aggressive and can get about 4 inches big and you can look into those too.  They are all compatible with each other and would recommend them.  Your 125 gallon tank can keep quite a bunch of fish considering these fish are small.  You can probably keep 30-50 3-6inch fish in that tank.  

-Matt-

---------- FOLLOW-UP ----------

QUESTION: hey Matt thank you so much for your answer earlier !! I finally purchased my new 120 gallons tank and put some fish in to cycle the tank. I have a question about the bacteria that the fish store tell you to put in the tank to help the tank cycle faster. Nutrafin vs bio-spira? which one do you think is better? and I'm planning to get another filter later on too so what do u recommend? which brand? and which one? I'm thinking about the elhuiem or fluval filter, I mean the canister one so which one do u recommend out of the two? and here is the list of the fish that I wanted to keep in my tank. 3 swordtails, 3 mollies, 6 corycats, 3 clown loaches, 4 rainbow sharks, 6 tiger barbs, 1 puffer. Can I do one of the cichild family in my tank? thank u so much for your help!!

Answer
Hi agian Jane,
It is not a problem, I like helping fellow aquarists.  When you cycle a tank its better if you use live bacteria rather than the bacteria they sell in cans in stores.  Some aquarists I know ask for used filter media from fish stores to "seed" their tank.  Do you have any friends that own fish?  You can ask them for their filter media if you are afraid the pet stores might be contaminated.  One good way to cycle with fish is to add fast growing easy plants such as Water sprite, Wisteria, Hornwort, or Anarcharis to soak up the excess nitrogen being released.  It will slow down the toxin build up in your tank.  Remember to do water changes in this tank also to prevent ammonia build up since you do not have ammonia-to-nitrite converting bacteria yet.  In time they will grow along with the nitrite-to-nitrate converting bactering.    

Both of those brands are good but I have heard more better reviews with Fluval cannisters.  Swordtails, mollies, clown loaches, cory cats are not aggressive, whereas sharks, barbs, and especially puffers are aggressive.  Puffers should not be kept with sharks or barbs either and should be kept alone or with other puffers.  In your case I would either keep non aggressive set, or the aggressive set without the puffer.  Cichlids are aggressive and will do fine with the aggressive set of fish.  
-Matt-