Got back in to this hobby about a year ago. Currently only have a 20 gallon tank, which houses 12 fishes, making it a community tank.
Things have been great but have to admit I have lost some due to not knowing what I was doing.
Fast forward and things have calmed down, without any others dying. Nitrate has been a constant battle which has led me to weekly water changes (50%). Also as of late but cutting how much I feed them in basically in half.
What it seems to be happening is that one of my Goldfish who is currently all white (used to be gray) is now turning orange. Is this normal?
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I am sure you’ve been told but common goldfish like the ones you have need 75gal or more each
You can’t even keep fancy goldfish in a 20gal without the risk of major issues
I can promise you that 12 fish in a 20 gal tank where some of them are common goldfish will give you trouble. A lot of trouble. If i were you, i’d rehome the goldfish to a pond and look into what can live in a 20 gal tank (that also is tall). Its not much really!
Yes, goldfish are messy as fuck so the water parameters and tank quality will suffer
Poor water quality is the most common cause of color change in goldfish.
You mention 50% water changes. If you really want to keep these goldfish, you probably need to step up to 80% water changes.
Goldfish are big polluters. In a 20gal tank, they are likely too much bio-load for that tiny bubble filter you have (unless there’s another filter I’m missing) to keep up with, and all of the fish are going to suffer.
Remember: the nitrifying bacteria that reduce harmful ammonia and nitrite to relatively less harmful nitrate only live on the surfaces of substrate in your aquarium. That means that your filtering capacity is limited by how much water passes through it, and your little filter is low-flow and small.
Unless you can add significantly more filter capacity (underground filter that pulls water through the gravel, or an external filter that pumps water through cartridges or high surface area media – which still may not keep up with these dirty fish), my recommendation would be to remove the goldfish.
All that aside, goldfish can also change color when they are growing very quickly. They will eat as much as you give them, and if they get more than they need, they will grow very quickly. There used to be a myth that they grow to the size of their environment, but I’ve seen them in a 55gal and remain one inch when fed sparingly, and also have seen them grow to six inches in a 10gal.
Goldfish are good starter fish because they jump-start the ammonia cycle and they’re relatively hardy. I don’t like them as long term community members because they’re dirty and can increase the workload for new aquarists, causing stress for other fishes and discouraging beginners from the hobby.
Edit: typos
Wow, amazing information. So there is one medium size airatior that sits on the bottom of the tank, producing bubbles. Also have an AquaClear HoB filter, rated for 30 gallons. Also a Green machibe but it only runs overnight on a timer
Yeah the goldfish were acquired since they are hardy as well as only being .75 cents! Been nice to see them grow bigger. But the store person said that they can be counted as “3-4” fish and I probably have overcrowded it.
Also have added some live plants several weeks ago but not sure if they are helping or not.
Testing for nitrates with a liquid test kit produces either dark orange to dark red results, which is bad
tl;dr even with the best filtration, you’ll probably still need to increase water changes to keep the goldfish.
*Typically if you have measurable nitrates, the ammonia cycle is where it should be.
Just a quick primer: there are specific bacteria that oxidize each form of nitrogen into less toxic molecules. Nitrosomonas oxidizes the ammonia into nitrite. Nitrobacter oxidizes the nitrite into nitrate.
Its likely that the necessary bacteria is healthy and in sufficient numbers, but filtration/flow is lacking – and this is the key point – for the bio-load in your setup. Water changes will be the only fix here.
I’d test for nitrite and ammonia just to rule out loss of one or more nitrifying bacteria. If you have measurable ammonia, you could step up water changes (frequency or volume or both), or remove the grubby, stinky goldfish.
Back in the 90’s, the local aquarium hobby store where I worked had around 1k feeder comets in a 55gal tank in the back. It was plumbed to a massive wet/dry sump that was full of “bio-balls” (the height of filter technology at the time) and pumped by a 1.5HP pool pump. IIRC, the total water volume was over 125gal. We had to change the water in that system every week to keep the water clear and clean.
Maybe its snobby of me, but it never seemed worth it to me to keep goldfish. I prefer Mollies for hardy fish, and they have more personality for my $.
Bonus: now I live in Central America, and swordtails and mollies nibble my toes when I swim in the rivers and waterfalls here! I would love to open a hobby store, but not sure if the government here allows it.
Amazing write up / information!
Any chance the store was Jacks Aquariums? Loved going there as a kid.
So all other perameters are good - (pH,nitrates and ammonia. Its just the nitrates that are bad.
I do have another 20 gallon tank. Would it be worthwhile and moving the three goldfish over here? Sounds like it wouldn’t be a good idea.
Once again thank you for the information
As the other commenter posted, a 20g just isn’t big enough to support them. But the fish in the existing 20 sure would appreciate if the goldies moved!
I worked at a different shop.
Some bonus pictures
Lovely kitty watching the fish! Hopefully they get along!
His name is Nico and is attached to me 24/7. He’s very friendly and just stares at the fish. Well so far…
