confusion about...

[Sharkychris]

I read recently in a fish mag in the letters section someone quoting a tank of 180x60x60 cm that should hold 269" of fish and the editor agreeing - this seems more than the 1 inch per gallon that i assumed was the norm from reading this forum. I also have a couple of books stating 30cm squared of surface area per cm of fish - this also seems more - i feel confused....

 

[Crookster]

Sorry, but I'm as confused as you. Everyone on here say's I'm overstocked, but the guy at my lfs says I'm not. I'm taking the safe option though and getting another tank.

 

[Crookster]

Did the mag quote cm or inches?

 

[Sharkychris]

yup, twas 6 foot by 2 foot by 2 foot so, 72x24x24 inches and he reckoned 269 inches of fish. I make that 175 us gallons i think..

 

[luxum]

The surface area calculation is more valid in my opinion. Tanks which have greater surface area can be stocked more heavily. A volume of water in a long configuration can be safely stocked with more fish than that same volume of water in a high configuration which results in less surface area for oxygen exchange. The old standby 1" per gallon fails to address that issue. By my calcs, 72x24 = 1728 square inches, divide by 12 to get 144 inches. I'm not sure how they arrive at a figure of 269, did they describe the formula they were using?

BTW Crookster, the guy at the LFS has a monetary interest in you adding more fish to your tank, he doesn't care if they die, that just means you'll come buy more to replace the dead ones. The people here have no ulterior motives, if most of them agree that you are overstocked, then you probably are.

 

[Crookster]

I've heard the surface area theory b4 and it sounds very plausible. What i don't get is, say you have a tank 50x50x50 it will have the same surface area as a tank 50x50x20, but you surely wouldn't put as many fish in the second.

 

[luxum]

You could, considering only oxygen exchange. Ultimately, it is the dilution of nitrates that is the advantage of more volume. You'd have to do more frequent water changes on the smaller system, and what individual species you stock has an influence on stocking levels. Some fish require a certain amount of gallons per fish, this is generally because they are big waste producers and need the volume to keep the nitrates diluted. That's why the guidelines reference only small bodied fish.

 

[smithrc]

stock levels are all down to experience... If i listend to the 1" rule i'd have an empty tank and an unemployed filter (ok not quite)

If you know what you are doing and keep a check on the chemical levels on the tank as you stock it (and as the fish grow) you'll know if your over stocked.
Good filtration is also important as the stack levels go up.

the surface area rule is also flawed... it all depends on the volume of water actually passing the surface. not just the surface area of the tank. if the surface was not agitated at all then very little oxygen would enter the water. however it the filter is constantly moving the surface with say a spray bar, Dramactcally more O2 will enter the water allowing more fish...

It's all about doing it slowly (and reading as much as you can find).

 

[CFC]

The inch per gallon rule is only a rough guide for newbies with standard size tanks stocked with average sized community fish, it is there to prevent over stocking by giving the novice fish keeper a line to work to. Once you move away from normal community fish into the realms of cichlids or just larger fish in general the rule starts to fail.

A experienced fish keeper with a good regular tank maintainance schedule can push the limits of a tank to around 2" per gallon provided suffiecient filtration is provided. Remember there are no hard and fast rules in fish keeping, what works for one person may not work for another so it is really just a matter of trial and error.

What i would say is if you are unsure of stocking levels for your tank then stick to the inch per gallon rule, once you are confident in your fish keeping and you know the limits of your tank then you can think about turning away from the rule and stocking your tank to the ammount you feel comfortable with.

 

[Sharkychris]

Many thanks for the views guys! the formula wasn't quoted - i was bit suss about that. I guess the most important thing i've learned is get as many views as possible am gonna keep my tank as is for the mo, dunno what id put in with 6 tigers anyway, dont really want a bloodbath....