Actual Tank Capacity

I was researching around the net and found an interesting article. People will take for granted that a 10 gallon tank will hold 10 gallons, a 20 gallon tank will hold 20 gallons and so on. This is a common misconception. It is not just water displacement from decorations and substrate that lowers the tank's capacity but the actual internal measurements are what matter. Say for instance you have a 20 gallon. That twenty gallon's external measurements will add up to about twenty gallons. But it is the living space of the fish that matters. Measuring the internal measurements and the 20 gallon actually comes out to about 16 gallons! Plus the decorations and substrate, you'll lower the capacity even more! So for a 20 gallon tank, you may end up with only 14 gallons, so you may be crowding your tank more than you think! Objections? Comments?

Thanks for bringing this up. Several months ago, the capacity error was discussed on our forum, and it seems like capacity in gallons is calculated based on the external dimensions of an aquarium, not how much water it will hold. I never considered that the substrate and decorations would decrease the stated volume even more. Still, most of us rely on stated capacity, and that probably works because aquarium keeping is not an exact science. Getting cheated IS an exact science.

hm,rightly you said both mr john and fishcrackrez....it is not a calculated science,and if you calculate correctly it never be the actual gallon that it is mentioned..forany tank it is not preferable to give 100% water of that tank,you shold provide some 1 inch below the top level of tank,and the substrate and filters come,so it is never the actula gallon it mentioned..

This may be a silly question but...
When gallons are used, are they US gallons or imperial gallons?
After measuring the inside of my tank it is 34 US gal and 28.5 imp gal. (not including filter or jungle).

I believe it would be in US gallons, since it was probably manufactured for the American market. You should be able to tell by the language of any labels, etc. Most of the remaining world uses the metric system. One of my history teachers said that's because the industrial revolution got going at about the same time in Europe and America. Europe went to the much more sensible metric system, and we stuck with part of an antiquated British system.

So, it's another useless fact of the day.

Actually it would have been made for the Thai market and has no labels anywhere. It would probably not be of acceptable standards for the American market as the glass thickness is only 5mm.
Anyway back to my question, perhaps it was worded poorly. When you calculate maximum number of fish in a tank do you use US or imperial gallons? If you have a large tank then the calculation will give quite an error if the wrong gallon is used.

You use US gallons, but the one inch per gallon rule is more general than specific. For example, some fish are short and thick, some are very active, some are aggressive, etc., etc. I have a 20 gallon tank with about 30 Red Wag Platies and a 40 gallon with two angelfish getting ready to spawn. It's really important to avoid over crowding, because the result is usually sick fish.

Somewhere on ask.com they have section about aquarium building. It gives material thickness versus aquarium height. Sorry I lost the specific address. The reason for my concern is that some aquariums are made for critters and will have thin glass. It's probably OK if it has already been used as an aquarium. I hope this isn't too much information.

PS: why not send us some pictures from Thailand.

Can never have too much information. I think most fish tanks here are only 5mm as it keeps the prices down. I've not looked at tanks for critters but i think i will be doing soon as the wife is asking for some terrapins now!
I'll sort some pictures in the next few days and try to have them ouploaded by weekend.

I always think of that region as having lush tropical vegetation and all that exotic stuff, but it's probably full of cities just like it is here in the middle of the Sonoran desert.

Thanks John, i've been scratching my head about what kind of pics, now i know
Some parts here are very lush. If you like green, this is the place to be.