Research Practicum on Goldfish Memory Span with 15 gold fish

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Registered Member
Sep 21, 2016
HEY so Im doing a project on Goldfish memory span (Comet tails). I plan on keeping 15 in a 20 gallon tank. I'm aware that its not a great idea to do that but I bought two 20 gallon filters, will start growing the bacteria, and other stuff to increase their survival and comfort.

I do not have the fish yet b/c I'm still nervous about it, but I want to know if this is okay? The project only runs 25 days and after that, the goldfish will be given to three different families and a school.

I will try to do everything in my power to give them comfort and reduce stress. Any advice is helpful :) And I want to know if this is okay (Keeping them in a 20 gallon tank for just 25 days, then after, each get bigger tanks in their new homes.)

I need an answer as soon as possible b/c in the morning i will buy the goldfish for the tanks.
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AC Members
Sep 22, 2016
Comet goldfish need at least 75 gallons (long term) for one for a long healthy life, you would probably need to do multiply daily 50% water changes to keep the ammonia down since the poop, a lot. I would suggest a lower number of goldfish, or a different type, like fancies as they need less water per fish (30 gallons for the first 10 for each after that). IMO it wouldn't be the best idea, they will be stressed, overcrowded and a good way for them to get sick easily.


AC Members
May 4, 2002
North Ga, USA
Real Name
As long as there is sufficient bacteria in the filter system and tank it doesn't help to add more flow if you plan on over stocking heavily as you are indicating. The problem is dilution of pollutants, and the nitrogen cycle only transforms the pollution into a less toxic for but it cannot remove it.

The size tank you have selected is not large enough for life that is a given, but as a holding space for test subjects it would depend on how much work you put into it. Daily or twice daily 50% water changes could make that work in the short term for the issue supporting life. Just how frequent the water changes need to be depends on how fast the nitrates build up. Aim to do a water change each time the nitrate gets to 20 ppm more than is in your source water (some sources can contain nitrate or even ammonia).


AC Members
Apr 27, 2010
So Cal
you could use some live plants -- external to the tanks if they would interfere with the experiments -- to keep the nitrates down. there are a number of you-tube videos on the subject, but basically they're all just a powerhead pumping water through a hose into a plastic container which holds the plants, with the return water just piped back to where it can fall into the aquarium.
you would want a fairly fast growing plant, maybe even grass, if all you need is a month of nitrate removal