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I want to buy an octo

Okay, i have a large tall octagon tank, and im pretty sure its around 30 gallons but i need to know how to measure the gallons. Can anyone help me out on that, and no i do not know the history of this tank but i went to a fish store the other day and the owner there told me that i can get it tested there for copper, can it be done? And can i use this octagon tank?
 
The area of a regular octagon is w^2-2b^2, where w is the width of the octagon and b is the length of the legs of the triangles formed where the edge of the octagon is the hypotenuse (as shown in the diagram). To calculate the volume of your tank in gallons, measure the inside dimensions w and b (in inches), and plug it into that formula. Now multiply that by the height of the tank (remember, in inches and inside dimensions). This number is the volume of the tank is cubic inches. 1 gallon is 231 cubic inches, so divide by 231 and that's how many gallons.
BTW, b = w/(2+sqrt(2))

In response to your copper question, I would not recommend using the tank unless you know for a fact that no copper-based medications have ever been used in the tank. I believe you can have copper tests done that are sensitive enough for cephs, but they cost somewhere around $60 (www.etrlabs.com). At that point you may as well buy a new tank. The copper test your lfs is offering is not going to cut it. Other than that, there is nothing inherently wrong with an octagon tank.
 

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Are you sure it is an octagonal tank? It is more typical to see six or five sided tanks than 8 (I have 3 hex and one pent). If my assumption is correct, you can easily get the center distance to flat side length in the formula below by pulling a measuring tape straight across from flat side to flat side and divide by two. If the tank actually has eight sides then the formula still works but determining the center to flat side distance is a little more difficult.

(length of 1 flat side inches) * (number of sides/2) * (center distance to flat side in inches) * (overall height in inches) * (.00433)

ex:
7" the flat sides of my tall skinny hex tank
x 3 there are 6 sides/2
x 6 flat side to flat side front to back = 12"/2

126 square inches
x50 tank height

6,300 cubic inches
x .00433 conversion multiplier for cu inches to US gallons
--------------------------
27 gallons (give or take)

How much water you actually put in the tank depends on what else you put in it to displace water (sand and other substrate) and how far from the top you actually fill it (leaving and inch and a halve to two inches empty is recommended for an octo).
 
Yea im sorry, the tank is a hexagon. Im sorry but im not good with math but i do have the measurements. All 6 sides are 10.5 inches in length, a base of 18 inches, and a height of 24 inches. Anyone wanna figure it out for me, thanks alot.
 
I should not do this... My own kids would ask, "What good is the stuff you have to learn in school?", and I would try to explain that everything learned will come in useful in one way or another in real life. With the instructions, you should be able to do this with a calculator if you will try it and not pass it off because "you are not good in math" :soapbox:

If by "base" you mean the flat side to flat side measurement then ...

10.5 * 3 (flat section length * half the number of the sides) = 31.5

31.5 * 9 (18/2 = half the base length) = 283.5 square inches

283.5 x 24 (height) = 6,804 cubic inches

6,804 x .00433 (conversion of cu inches to US gallons) approximately: 29.5 gallons

Is it acrylic or glass?
 
Well sure i know math but it seems complicating to find the volume of a hexagon, so thanks for telling me. Now a 29 gallon hexagon tank should be fine then? Whats the best method of cleaning out the tank because i would like to get this tank up and runnin soon. I heard you shouldnt use bleach.
 
I read a biography about Thomas Edison and one of the first challenges he would give a new engineer would be to determine the volume of a light bulb. His ultimate solution after the engineers pulled out their hair and came up with all kinds of mathmatical solutions was to take off the end and fill it with water then dump the water into a measuring device. Sometimes practical solutions are the best when there are unknown interferences (in the case of the bulb, the glass and shapes were not always consisent). On the other hand, it is good to be able to look up and implement a mathmatical solution as a balance check or to predetermine a value when the "bucket" solution is not viable.
 
robind;142370 said:
All you need is some calculus :wink:
In a perfect world yes and why they insist on teaching plane geometry as early math for surface areas/volume rather than calc is beyond me. However, the only way to actually know how much water you put into an aquarium with LR and sand and whatever is to follow Captfishes suggestion. Calc/geometry will give you a good idea of how much you CAN put in (so you know how much to make up) but measuring is the only way to find out how much you DO put in.
 
dd

Well thanks for the math lesson :nyah: never knew that. So id like this tank started this weekend, what would be the best method to clean out the tank as best as possible, and then how should i start; add the saltwater, add the sand, and start the filters?
 
I use a pressure washer and Mr. Clean erasers. If it is a glass tank you can buy a metal scraper or use a razor for the difficult algae/buffer (be very careful around the silicone - algae is better than a leak).
 
Alright i have a magic eraser and i have a razor blade scraper so ill clean it as best as i can. Also, on one side of the tank there a couple cracks, any suggestions on how to fix it? Should i replace it or can i do anything at home that can fix it. For my other fish tank there was a big hole on the bottom so i just used duck tape and taped both sides up and it was fine, can the same be done here?
 
I would be terrified of a crack, there is alot of pressure pushing against that glass when it is full of water. My opinion would be to replace it, or use it as a reptile/arachnid tank.
 

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