Why do my oranda red caps and my black moor eat air bubbles?

Question

I own a Oranda red cap and a black moor both very young only a couple of months.
I have a Bio orb tank thats only fifteen leters.
is it true that they will only grow to the size of the tank?
oh and yes why do they eat the oxygen bubbles?
thank you for your help.

Answer 1

and to answer your eating the bubbles question, They are not really eating the bubbles, though they think they might be. Because where goldfish are in the cycle of life, they will try just about anything for food. Things that are most enticing to most fish is something that is moving. They probably think they see something moving amongst the bubbles(when you and I know it's just all bubbles) so their first reaction is to catch it. Goldfish are always foraging for food. This doesn't mean they should be fed when you see them do this, they really don't need it. It's just their nature. They are not starved for oxygen either and the air bubbles won't harm them. For them, it's just something to do.

Answer 2

15 liters = 4 US gallons

That's not a good size to keep two goldfish. They might be okay for now because they're small, but they'll need larger in a few months. The other person answering about stunting is correct. See this link for more explanation: http://freshwater.fanatics.googlepages.com/fishstunting

Your fish are probably trying to eat the bubbles because they think they're food.

Answer 3

No, goldfish will die if the tank is too small to accomodate their natural size. If the tank is too small, their organs will continue growing, causing them to die since thier outsides can no longer grow. Yours sound small, so you may have time til you need to upgrade. A 28 gallon should be plenty big to accomodate two adult size fancy goldfish as long as you add nothing more.
As for oxygen bubbles, I have never heard of this. Are they getting enough oxygen in your tank? Mine is in gallons, but 15 Liters doesn't sound very big.

Answer 4

yes they will only grow to the siize of the tank but this is a bad thing. Its called stunting, when the outer body stops growing and organs keep growing, its very painful for the fish and they die from it

Edit:for some reason I thoguh you said you had like 4 re caps
so a 29 gallon-30 gallon should be good

Answer 5

No it isn't true. Gold fish will continue to grow. Your fish should get to around 8 inches each. 15 liters is ok for now but they will need to be rehoused in a few years.

The Oxygen bubbles, more than likely they thought it was food.

Also, You can supplement their diet with things like Lettuce, mustard greens, turnip greens, collard greens, spinach, peas, endive, seaweed, cukes, kale, chard, broccoli, lima beans, green beans, etc. and feed aquatic plants (e.g. duckweed, azolla, salvenia, etc) or hair algae daily.

For their Carotenoids which are a family of pigments the fish can't make themselves and are obtained as part of the diet. These pigments result in red, yellow and orange colors. Fish have cells called chromataphores. Those cells convert lutein and carotenes into astaxanthin which is the red pigment.
sources include, brine shrimp, krill, spirulina, marigold flowers, paprika, sweet red peppers, yams, carrots, pumpkin

Watermellons and oranges are also good as well as proteins like chicken (chicken livers) beef (livers and parts) and pork as well as worms and bugs.