Agressive Fantail Black Moor Goldfish

SiobhanRae2016October 8, 2013

So Im a college student and have two Black Fantail Moor goldfish in a 10 gallon tank on my desk. Everything was going great (I've had both fish for several months) until I noticed Othello (the larger Moor, about 4-5 inches long) started to be agressive in short spurts toward my other, smaller (about 2-3 inches) Moor, Ella. He will buffet her with his fins when I put food in, chase her about the tank and push her around; even to a point of flipping her upside down and shoving her to the top of the tank.

Ive only seen it once or twice but it really concerns me; I'm at classes and activities for most of the day and while I return to my house regularly to drop off books or whatever, I dont see them every moment of every day. Most of the time they get along okay, swimming about and poking the bottom, but when it happens its very disturbing and I've been scared tot he point of intervention twice by rapping on the glass and even poking Othello gently when he was basically barrel-rolling poor Ella around the perimeter of the tank.

Is this a common behavior for goldfish, maybe Moors in particular? I've had fancy tailed goldfish in the past before Ella and Othello, and tetras, goldfish and gobies in the distant past, but I've never seen aggression like this. Are they just playing and I'm overreacting? Any thoughts on the matter would be great!

A Worried Goldfish Mom

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Sorry to tell you but ten gallons is way too small for a fish that will reach 10-12 inches at maturity - it is a myth that a fish grow to fit the size of the container and its really sad that uninformed pet store employees are not giving correct information.

I was going to guess spawning, but Im thinking its more likely to be competition due to space issues. This spring I bought some comets recently for my pond - the cheap ones that are crammed hundreds into a small tank and one of them was in a frenzy chasing and butting against the others especially around food He's calmed down totally now that he's in the pond with plenty of space and bugs to eat and in fact has grown huge over the summer.

There are some great goldfish-specific forums and websites - I'd take a look at those. If you cant afford a larger aquarium, consider re-doing your set up as an indoor pond. There are some smaller 30-40 gallon stock tanks that could be used (would not go smaller than that - 20-50 gallons per fish is whats usually suggested for full size pond goldfish. That plus a small 75-100 gph pondmaster or tetra pump + filter would be under $100.

    Bookmark   October 8, 2013 at 11:24AM
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If you want to keep both fish, I suggest buying a larger tank for the large Moor and separating them, or finding a new home for one of them. Your local fish store may take one back and and give you store credit.
If the aggression continues the smaller fish will die, either from injury, starvation, stress or a combination of all 3.

Be sure and check your water parameters. With 2 fish in a 10 gal tank the chemistry of the water can quickly get out of balance and can cause fish to act differently.......and will eventually kill them.

    Bookmark   October 8, 2013 at 2:17PM
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