20 Gallon Tank 3 baby comets -- is 20 gallons enough [TEMPORARY]

BIG GIGANTIC DISCLAIMER/BACKSTORY:

My husband and I are in the process of planning out a 400+ gallon pond in our backyard. I have 1 comet goldfish (full grown, circa 2017) in a 75 gallon tank. He had a tank mate up until 2 weeks ago when he suddenly passed (RIP Jiminy) after I rescued him 4 years ago. I have (begrudgingly) come into ownership of 3 baby comets about a week ago. They've been in a 20 gallon storage bin/temp tank for that duration. All of these fish will eventually go into the pond, when it's finished next year!

My Current Dilemma:

After they are quarantined, I plan on adding at least one of these new comets to my 75 gallon to be a companion for my remaining comet, Paul Rudd, as she's been lonely. This will leave 2 comets in a temporary tank until it's time to put them in the pond.

1. How long, realistically, can I keep these other 2 goldfish in their 20 gallon tank? They are currently all 1-2.5 inches in length, so they're very small.
2. OR, should I move all 3 into the 75 gallon?

I'm trying to do the best for all of them. Fish per gallon of water, would separating them half and half be better, or would adding them all together in the big tank be best? Any advice or tips would be super appreciated!

 

Sounds like you have a plan because Comets should be in a pond. I would say as long as the fish are small the 20 will be OK temporarily. But, I would put them in the 75 when the quarantine period is over: Goldfish are "social" creatures and they can keep each other company.

 

Sounds like you have a plan because Comets should be in a pond. I would say as long as the fish are small the 20 will be OK temporarily. But, I would put them in the 75 when the quarantine period is over: Goldfish are "social" creatures and they can keep each other company.

Okay, so you would keep all 4 in the 75 after the new 3 have finished quarantine? I would much rather do that than have 2 tanks to take care of, but I was just wary because I know, even if they're small, goldfish put out so much waste and I don't want to put my OG goldie in harm's way. Just asking for clarification!

 

Okay, so you would keep all 4 in the 75 after the new 3 have finished quarantine?

Yes, temporarily,...while they are small.

 

Ive had a feeder comet go uneaten and reach 6" in a year of growth in a 72g with other larger fish when I put him in as a feeder, they just wouldn't touch him.

4 comets wouldn't be much of an issue in the 75g, until that point, then it starts getting crowded. You can still go a while longer with more water changes.

If you intend to move to a pond that will be a few hundred gallons in a year or so then likely they won't ever get so big it becomes a lot of work maintaining water quality in the 75 in my opinion.

They should grow 1-4" the first year of life, then 1-2" or so each additional year after that until topping out either through frequent small feedings each day to maximize mass and growth, or just time until they reach max size.