Number of goldfish in a 40g tank?

[0Louis0]

My question is in the title, I really want to keep the largest possible number.
According to many websites, it should have only 4 goldfish. What is the reason of such low number? Is it because they produce much waste? What if I have a good filter with much water changes?

 

[librarygirl]

It depends what type of goldfish. For fancies you could do 3 (general recommendation is 20 gal for the first one, 10 gals for each additional). Comets, commons and koi belong in ponds as they get far too large for home tanks. Yes, goldfish are very messy and grow rather large as well. For filtration you want at least 10x the filtration for your tank, so for a 40 gal you want total filtration for at least 400 gals.

Here's a guide a member on this forum wrote: http://www.myaquariumclub.com/goldfish-101-11174823.html
Also if this is your first tank you'll want to read up on cycling: http://www.aquariumadvice.com/guide-to-starting-a-freshwater-aquarium/

 

[jlk]

Hi! Welcome to AA!! With messy goldfish that grow quite large very quickly and carry a huge bioload (produce alot of ammonia), you want to keep the smallest number possible. For a 40g, three fancies is fully stocked but you may need to upgrade this further as they grow. An adult moor (for example) thats 10-12+inches would be a bit cramped in a 40g by itself. For single tail goldfish (commons, comets, shubunkins, etc), a single one would fully stock the tank but a pond would be more suitable environment.

In respect to filtration, you want minimum of 10x the tank size or 400gph though heavier filtration would be preferable. Heavy filtration does not eliminate the need for big water changes- these are a must with messy fish.

Heres more info on goldfish and their care- please ask any questions!

http://www.myaquariumclub.com/goldfish-101-11174823.html

 

[Cbcrash]

I have 2 5 inch fantails in a 75 along with 2 smaller ones and I have 9 fancies in another 75. No one follows the 20 gallon per fish rule.

 

[Cynic]

I have 2 5 inch fantails in a 75 along with 2 smaller ones and I have 9 fancies in another 75. No one follows the 20 gallon per fish rule.

Don't pass off your personal beliefs for fact. The 20G rule whether or not you adhere to it has far more basis and reasoning than just what you do.

 

[Cbcrash]

My fish have lots of room and are active and adorable. I love em. The fish stores don't abide by the rule either, restaurants too etc. I know what I'm doing and I'm in fish keeping for life

 

[jlk]

I have 2 5 inch fantails in a 75 along with 2 smaller ones and I have 9 fancies in another 75. No one follows the 20 gallon per fish rule.

Just because you decide to overstock your tank does not mean you should be suggesting it to others asking for advice. Nine fancies in a 75g is recipe for disaster waiting to happen. Maybe you should reconsider your suggestions considering all thehealth issues you have had with your fish. Less is always more with messy fish that grow quite large. Comparing a lfs that stocks multiple fish in small tanks vs a home aquarium is comparing apples to onions- they run massive central filtration systems and the fish are never meant to be there long term. We keep our fish for life so striving to provide them the best conditions should be our goal as responsible caregivers.

 

[Cbcrash]

My fish guy says im not overstocked and every one I ask. He has been into fish for 40 yrs so I trust him. I won't have a tank with 3 fish in it. I'm doing the right thing

 

[0Louis0]

Okay thank you Cbcrash.
But to others who are against this, what can happen if I put more than 3-4 like you said? Would the fish not grow to their biggest size (but still live) or die because of space or just ammonia level might rise?

 

[jcolon]

Okay thank you Cbcrash.
But to others who are against this, what can happen if I put more than 3-4 like you said? Would the fish not grow to their biggest size (but still live) or die because of space or just ammonia level might rise?

It's pretty simple ... it all comes down to how much more work you'd want to put into tank maintenance and PWC's. Goldfish do produce very large bio-loads so putting say 5 in a 40 will almost certainly require 50% PWC's ... figure 2 -3 times a week.

Common, comets and Koi would almost certainly get stunted growth in 40gal ... not very pleasant for the fish. They really are more suitable for ponds. Drives me nuts when I see feeder goldfish by the hundreds in those large tanks at some LFS's. I've yet to see one with healthy looking goldies ... they never look good. 4 fancy gold fish in a 40gal is doable, just requires diligence on PWC's and filter maintenance, 3 would make just make it a bit easier. Keep in mind, fancy goldfish can grow to nearly the size of a tennis ball.

 

[Cbcrash]

If you put more than 3 in a 40 gallon, it all depends how big the fish are and what kind of fish. U do need 2 power filters. At least 400 gph. The size of the tank matters too. Get a rectangle instead of a bow front or a hexagon. The rectangle has more surface area. I also use reverse osmosis water so there is no contaminates like chlorine or heavy metals, like in tap water. If u use tap water, use a dechlorinator. I like Seachem prime. Make sure ur tank is cycled, and don't put 3 fish in at one time. Do one a week after ur tank is cycled. Buy a test kit to check water before adding fish. 40g is ok for 3 fish, if u do everything right, u won't have to worry about ammonia poisoning. My tanks are both 75 gallons, I have power heads to circulate water and have bubblers breaking the surface, and I have lots of filtration. 9 is not too many for my tank. They have plenty of room to swim. When they get bigger il buy a bigger tank. Good luck

 

[jlk]

If you put more than 3 in a 40 gallon, it all depends how big the fish are and what kind of fish. U do need 2 power filters. At least 400 gph. The size of the tank matters too. Get a rectangle instead of a bow front or a hexagon. The rectangle has more surface area. I also use reverse osmosis water so there is no contaminates like chlorine or heavy metals, like in tap water. If u use tap water, use a dechlorinator. I like Seachem prime. Make sure ur tank is cycled, and don't put 3 fish in at one time. Do one a week after ur tank is cycled. Buy a test kit to check water before adding fish. 40g is ok for 3 fish, if u do everything right, u won't have to worry about ammonia poisoning. My tanks are both 75 gallons, I have power heads to circulate water and have bubblers breaking the surface, and I have lots of filtration. 9 is not too many for my tank. They have plenty of room to swim. When they get bigger il buy a bigger tank. Good luck

Unfortunately, your fish are not going to get 'bigger' with an overstocked tank. If you have had them for years as you mentioned, they are already stunted. Heavy filtration does not make up for lack of sufficient water and space.

 

[Cbcrash]

I'm fine with my fish not growing anymore cause I can't afford a 220 gallon tank. They are so cute anyway. I don't want them any bigger.

 

[Samzter]

I'm fine with my fish not growing anymore cause I can't afford a 220 gallon tank. They are so cute anyway. I don't want them any bigger.

Those fish, are supposed to grow! You have shortened the lifespan of these poor fish drastically... This will cause them severe pain. You can't pick and choose the size of your fish. Next time do some research before buying them

 

[Cichlid Kid]

So let me get this straight Cbcrash, your willing to sacrifice your fishes health (stunted growth and eventually organ failure) just for your viewing pleasure? UNREAL

To the o.p. Listen to these others here. They are trying to help you and your fish. JLK especially has countless years of experience with goldies and would not give sub-par advice.

 

[Cbcrash]

I'm in fish keeping for life and mine are fine. They have plenty of room and swim. I am
Very knowledgeable and change water once a week, half the water, I know what I'm doing. I won't change how i care for them.

 

[Samzter]

I'm in fish keeping for life and mine are fine. They have plenty of room and swim. I am
Very knowledgeable and change water once a week, half the water, I know what I'm doing. I won't change how i care for them.

If you knew what you were doing then why are your fish suffering? Regardless of what you say they are suffering

 

[Cynic]

I'm in fish keeping for life and mine are fine. They have plenty of room and swim. I am
Very knowledgeable and change water once a week, half the water, I know what I'm doing. I won't change how i care for them.

You're confused how stunting works. Their bodies don't grow but their organs do. They die. The myth that fish grow to their tank size ignores the dark side of that equation.

 

[0Louis0]

Ugh just 3 or 4 goldfish in my tank makes it so empty.. not theoretically but what it looks like from outside.
I already bought a test kit, 2 strong filters and was getting ready to buy many fish and fight to keep my water clean. But this pain thing ruins it all
Cbcrash seems to have pretty long experience too, but there are so many criticizers

 

[Cbcrash]

What kind of fish and how big are they ? What kind of filters? Ammonia should be 0, nitrite 0, nitrate below 20, ph and high range ph all depends on the fish u have. When u do water changes, rinse the filter media in the water u take out, so u won't lose bacteria. And change filter pads once a month, the carbon in the filter pad keeps the water clear, along with odors.

What's being a pain?