how many is too many

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tracylynn

Aquarium Advice Newbie
Joined
Aug 4, 2012
Messages
6
My nephew gave me a 20 gallon hex tank with 5 mollies (all but 1 under an inch long) and a neon... so I bought 2 flying foxes (to keep tank clean) and 3 more neons because I heard neons did better in schools. However, now I have 11 fish in a 20 gallon with plants... I don't want them to start fighting. What's the rule of thumb on how many is too many?
 
The most know is 1 inch per adult fish per gallon. It is a very inaccurate rule but can be used with a grain of salt. In example, the bioload of a neon tetra is so minuscule that they don't make much of a difference. Another fault in the rule is taking into account a tanks "footprint." Some tanks are taller than they are wide creating a smaller footprint for less swimming area. With your current stock I would most likely say you are at the limit, maybe add another neon or two but nothing else besides that. Also if your fish breed don't raise the fry in that tank
 
Please do not reference the 1 inch per gallon rule. Most fishkeepers scoff at it because it's entirely unreliable unless you're talking about very tiny fish. You need to consider bioload, environmental species needs, compatibility, school requirements, etc. when stocking a tank.

You will need to return the flying foxes. They require a larger densely planted tank. Also, flying fox should be kept as one per tank. They get very aggressive as adults and have been known to kill mollies and other same-sized fish.

Neon tetras are a schooling fish and require a group of at least 6, 8 is better. With the mollies, you don't have room for a school of tetras.

Your tank is actually overstocked right now.
 
Agree with LyndaB. Plus ... Correct me if I'm wrong, but hex tanks tend to be fairly tall at the expense of horizontal swimming space.
 
Exactly. Any tank with a weird shape cannot be considered to be a true (insert size) gallon tank. This tank is probably equivalent to 15 gallons, if that. You just don't end up with the same real estate.
 
LyndaB said:
Please do not reference the 1 inch per gallon rule. Most fishkeepers scoff at it because it's entirely unreliable unless you're talking about very tiny fish.

The op asked what a common rule was, I responded with the most common rule there is and then went on to say that that rule is very inaccurate.
 
Thank you for all of the tips... I'm kind of upset at my local aquarium store because I went in to purchase a tiny pleco & the sales clerk talked me into the flying foxes explaining that they will stay small and are compatable with the fish I have.
I do believe they have a no-return policy.
I have a large, indoor goldfish pond at my work... how do you think the foxes would do in there?
Or... I have a 6 gallon rectangle tank with 2 goldfish in it... should I put one or both of the foxes in with the goldfish? Maybe separating them would help?
Any advice is very appreciated...
 
There definitely isn't room in the 6 gallon for the flying fox. As stated, they need a larger tank than 20 gallons. Also, the six gallon is much too small for even one goldfish. For fancy goldfish the general rule is 20 gallons for the first fish and 10 more gallons for every additional goldfish. They have a very large bioload and get very big. I'd add these to the goldfish pond. I'm not sure how the flying fox would do in the pond, as they are tropical fish and like warmer waters than goldfish do.
 
any good lfs should take returns provided the purchase was made recently. if your store won't take them I would suggest finding another one.

I would agree that you're overstocked. mollies will grow to 2-3" and swim all over the place.

I agree that you need at least 5 tetras for a school.

after you lower your population of fishes, you may want to add some bottom dwellers like cories or shrimps
 
As a side note, the plecos mostly aren't tiny. If you are going to look into getting one, check out Bristlenose / Bushy Nose Pleco Ancistrus, they stay smaller 5-6 inches but still have a big bioload, need a big tank, 50% weekly water changes for good health.
 
in a tall tank like a hex 11 fish realy isn't much
but
yes theres a but
there is many factors mollies and neons are both middle to top swimmers so over crowding could be a issue in time
as of now you have 5 mollies (remember they breed like rabbits) you will need to thin the heard every now and than
4 neons
and 2 flying foxes they swim about everywhere top to bottom and will grow in time and most likely need to be rehomed
but
yes another but
remember most pet stores will trade fish
so thats a plus at the moment
but
yes one more but
you have a bare bottom you can add a few small bottom dwellers to fill a void maybe 3/4 small dwellers at best
concider a hex as a 3 story condo you already have the two top floors filled to capacity and nothing on the ground level
 
Thank you everyone.
So I'll "give back" my flying foxes to the store & pick up 2 more little neons.
The mollies are all female so there is no breeding issues.
The goldfish in the little tank will be going to the goldfish pond when they get bigger. They're too small right now.
I'm really glad I joined this site.
Maybe I will be able to help someone after I learn a little more.
 
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