How many fish in a tank?

[Wilhelm]

Is there a formula for safely estimating the number of fish that can be placed in a given tank? I have a 120 gallon tank with 120 pounds of rock and 120 pounds of gravel/crushed shells. Dimensions are 48" left to right, 24" front to back and 24" top to bottom. I currently have seven fish, none longer than 3.5".

Thanks

 

[Deanos]

There is no formula.

 

[hijinks]

The one thing I have read is place only 1 fish in at a time.. wait to see if the bio load is ok.. if it is you can add another in a few weeks.

 

[Wilhelm]

I remember referring ages ago to a formula for fresh water fish linking inches of body length to square inches of tank surface area or footprint and was wondering if such a formula existed for marine tanks. Thanks for the responses.

Wilhelm

 

[NYreefNoob]

formula is are the fish happy and safe, will your system handle the bio load and is skimmer enough to handle, i personally have 8 fish in a 60g cube, also depends on what type of fish you plan to keep or have

 

[mray]

The less fish you have, the longer your tank can survive in a blackout.

 

[MikeyZO]

I agree with the above. That being said, here is a guideline, but i would stll follow recommendations as above also.
http://www.3reef.com/aquarium_calculators/

click fish capacity

 

[cali_reef]

You'll end up with the right amount eventually :lol2:.

 

[Wes]

the formula uses the following variables

nutrients, agression, stress

any of those 3 variables begin to rise you probably have added 1 too many.

For example. My filtration could probably handle another fish. But a newcomers get their butt kicked. When a new radiant wrasse was ganged up on an murdered by everyone, I realized i reached my limit.

 

[KathyC]

I agree with the above. That being said, here is a guideline, but i would stll follow recommendations as above also.
http://www.3reef.com/aquarium_calculators/

click fish capacity

Lova ya Mikey, but that calculator ought to be blown to bits. According to it my 120 should be able to hold 29.88" of fish..in length. That is absolute nonsense . (Admire your intent though!! )


First off - when trying to figure out how many fish you can safely put into a tank you need to take their ADULT SIZE into consideration..NOT what size they are 'now'.
If you put a fish that should ultimately grow to 9" into a tank that is too small to accomodate their adult size, their body will still attempt to grow to it's proper size but it may fall short and be slightly stunted. It is a myth that a fish will only grow to fit the size tank it is raised in. What happens is some part of the fish, often one or more of its internal organs will not attain full size which will reduce not only the quality of it's health but also the length of it's life.

Secondly, and I'll give you an example for this one...
I have 2 fish in my tank that are both about 4 1/2 inches long..
Here is one of them:

Here is the other:

Huge difference in body mass. That must be taken into consideration too!!

Always pre-plan, know what you are buying and you should be fine. Don't go by 'inches', use mass instead. The lighter you stock, the easier it will be to maintain your tank

 

[h20 freak]

120 pounds of gravel/crushed shells.

Thanks

I'm sorry to hear that.

 

[basiab]

There is another difference and that is how much the particular fish adds to the bio load. Some fish are neat and others are messy. So even the same size fish does not produce the same amount of pollution.

 

[LeslieS]

Consider what type of filtration you have and how often you want to do water changes.

Also, some fish like to hide all the time and some fish like to be out in the open. Your tank will look fishier and more active with fish that like to be in the open. My tank looks like it doesn't have any fish because they all hide, but they are still there adding to my bio load :-(