Newbie here (please be gentle) I guess a Biorb is probably not a proper aquarium to you Guy's, but my lad broke my aquarium, that he had pinched for two homeless goldfish (that’s another story), My darling wife who now treats the fish as her little babies (Yeah, I've now dropped below two goldfish in the household pecking order) then went on Tinternet and decided that she wanted a Spherical Biorb. I got one from FleaEbay. unfortunately the Biorb tank came without a pump and when I connected up the pump that I had from a conventional aquarium it would not blow bubbles through the Biorb filter built into the bottom of the tank. Does the pump have to work at a higher pressure, or have I got a blockage? There is a small capsule in the air pipe clipped into the bottom of the base, does any body know what that does?

Incidentally I've currently got the aerator-filter unit for a flat sided tank hung from the brim of the Biorb which works fine and is quieter than our old setup as I've made a top from an old plastic paint can, yeah I'm tighter than a ducks ___, Two 'free' goldfish have already cost me a new aerator-filter unit and second hand Biord! The fish seem to be much more active in their new tank and do not seem to be having a go at each other now?

I'll be the first one to say it...
Most Goldfish get HUGE. I do not know what type you have, but more likely than not you have a type that will get big. That being said, If I were you I would not worry about getting your bubbler to work as much as where to get a bigger tank. Most Goldfish require a minimum of a 20 gallon tank. You have two, so I would guess they would need at least a 30 gallon tank. Basically
Goldfish may only grow to the size of the tank they are in, but their insides will continue to grow beyond that making life painful for them.

As far as your initial question goes, you probably need to replace the tubing in your set up.

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75 Gallon Planted

exactly what he said :D

Pete has used other airpumps with biorbs in the past with no problem as the only real difference is that you can plug them into the biorb plug adaptor. If using another airpump make sure that it is 100 l/h minimum and that your airstone has been replaced as this can clog.

Thanks Guy's,
How big can I let the fish grow before I need a new tank?

well most people recommend a 20 gallon tank per one goldfish and then another 10 - 15 for each other added to the tank. So you minimally need a 30 gallon tank.

I am of the opinion that you need a 30 gallon for the first and then another 10 for each other so I would recommend a 40 gallon tank.

Some goldfish get to be 14"+ Some of the more common ones will max out around 6 - 8". Realize that goldfish produce an absurd amount of waste which is why you need a good amount of space.

You really will not be able to keep them in the tank long. I'd give it 3 weeks to a month max. More towards that 3 week mark. Depending on how big they are already that may already be no enough space for them.

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Thanks JBrown,
I've just realised that Biorb do a mini tank, fortunately mine is a 30 litre and the fish are about 3" so I hope they might be OK for now. Although they do chase each other round at feeding time!