1 fish per 10 gallon rule?

[aquadon2222]

So I have a big 320 gal cubic tank and would like to have 32 discus fish in there. (trying to get 1 of every strain that our vendors sell. I'm at 26 now - they look comfortable, have their space and eat like pigs, so hopefully just a few more won't mess things up. )

So my question is do you think that's too many? I've read 1/10gal and have even read 1/6gal from a reputable dealer on SD, (which would put my max at 53 fish! Too many, even for me. I'm not trying to breed them or grown them out to max potential, rather, I'm in it for having a colorful aquarium with healthy fish with good size, shape and health.

[Second Hand Pat]

If you calculate the volume using the inside dimensions of your tank you will found it is not in fact 320 gallons. As for number of fish I personally do not like to walk the boundary of having a overstocked tank ie. in case of a power outrage I do not want to panic with an overstocked tank so my tanks are actually lightly stocked compared to most.

[adapted]

Common sense would indicate that one-adult-per-10-gallons is at best a VERY generalized rule of thumb. It's easy to remember, easy to communicate to neophytes.

But it ignores water change, feeding, tank maintenance and tank geometry variables, as well as actual size of the adult fish. (4.5" adult, or 7.5" adult?)

The hobby needs a ready answer to the "How many?" question from beginners and "one per ten gallons, but no less than 5/6" is the answer that has been settled on. In reality, the question should get a paragraph-length response, with lots of conditional clauses.

[OC Discus]

Think about the non-discus rule of 1 gallon per inch. The shape of discus would double their requirements. If a non discus is 6" long, it might be 2" high. It would get six gallons. But if a discus is 6" long it is also 6" high- 2 or 3 times a non discus. Does that mean the 6" discus should get 12-18 gallons of water?

Clearly there are variables- primarily filtration and water changes. Just like planted tanks- it can be done, but requires more effort to do it right. Someone could overstock a tank, but they would also need to over filter to maintain water quality.

[nc0gnet0]

I got this..........

First calculate the total bio-mass in grams cubed. Then divide by actual tank volume in liters over the total milligrams of food fed, multiply by the volume of water changed per day. Take this number multiply by pie r squared and then add 2.

When the beginner looks back at you with a blank look on his/her face, tell them roughly 1 discus per 10 gallons.........


http://smileyshack.files.wordpress.com/2011/09/crazy-34.gif?w=700&h=

[yim11]

The hobby needs a ready answer to the "How many?" question from beginners and "one per ten gallons, but no less than 5/6" is the answer that has been settled on.




When the beginner looks back at you with a blank look on his/her face, tell them roughly 1 discus per 10 gallons.........




There ya have it...

lol

[nc0gnet0]

In other words...............

KISS :)

[adapted]

You could make it even simpler: tell everybody who asks to get six. Period. No tedious multiplication/division involved. When they die, get six more.

[Caitie]

You could make it even simpler: tell everybody who asks to get six. Period. No tedious multiplication/division involved. When they die, get six more.

That is not very good advice. Nor a solution at all.

[aquadon2222]

I got this..........

First calculate the total bio-mass in grams cubed. Then divide by actual tank volume in liters over the total milligrams of food fed, multiply by the volume of water changed per day. Take this number multiply by pie r squared and then add 2.

When the beginner looks back at you with a blank look on his/her face, tell them roughly 1 discus per 10 gallons.........


http://smileyshack.files.wordpress.com/2011/09/crazy-34.gif?w=700&h=

Haha, so true. Fortunately, I'm degreed in physical chemistry and biochemistry and can calculate a more accurate measurement than the 1 fish/10 gallon rule, which we know to be a VERY rough rule of thumb. First problem is "how big of fish are we talking about?" Next is the physical reality of biomass that the length of a fish isn't a liner relationship to its weight, i.e. a 6 inch discus weighs a lot more that twice the weight of a 3 inch juvie...alot more. (There is actual a formula which calculates weight by length x girth squared which is pretty accurate, but I digress.

So, I'll simplify my question:

What signs might I look for that would indicate an overcrowded tank? My tank is thriving, water quality perfect, and I am close, if not at already, to my max # of fish based on the eye test.

The only thing that I have noticed is a slight increase in the "peck, chase and tag" game: should I view this as typical playful behavior, or "get out of my space"?

[OC Discus]

You should be good with 32 in a 320. Obvious signs of problems are declining water quality and/or sick fish. As long as you can keep up water quality, proportions should be the same: 5 in 50 gal, 10 in 100 gal, 30 in 300 gal 100 in 1000 gal. Heavier stocking would require more maintenance/better filtration to keep water clean.