adding fish to the tank?

mbattles22 · Jun 23, 2010

Just wondering if there is a limit to the number of fish you can/should add to your tank at a time?
Thanks for any insight!!

110reef · Jun 23, 2010

Adding fish to the tank upsets the bio system. For example, if you have one small fish in the tank, there is enough bacteria present to consume the wastes that that 1 fish puts out. If you put another fish in there, you double the load. It will take some time for the bacteria to catch up with the new load, and so you will have a mini-cycle take place. However, if you have 30 established fish, then the bacteria population is there to balance the load of 30 fish, and adding 3 more only increases the load by 10%. Chances are you would never see a cycle from that.

So the answer to your question really depends on how mature the tank is, the current level of bioload, and how big the new fish are.

mbattles22 · Jun 25, 2010

110reef said:
Adding fish to the tank upsets the bio system. For example, if you have one small fish in the tank, there is enough bacteria present to consume the wastes that that 1 fish puts out. If you put another fish in there, you double the load. It will take some time for the bacteria to catch up with the new load, and so you will have a mini-cycle take place. However, if you have 30 established fish, then the bacteria population is there to balance the load of 30 fish, and adding 3 more only increases the load by 10%. Chances are you would never see a cycle from that.

So the answer to your question really depends on how mature the tank is, the current level of bioload, and how big the new fish are.

Well we have a 120g that has been running since Nov. 09'. We currently have 14 fish. Most have been around for several months....the newest additions (4 bar gobies) for about one month. We were thinking of adding 4 more fish in the next 3-4 wks. Do you think we will have a problem? If we do a 5% water change twice a week instead of a 10% once a week, will that help things out? Thanks!!