If you are going 3' deep than your tank is about 740g if I am getting your dimensions correct. That is a good size tank.
I am pretty sure 1/2" acrylic is not good enough for 3' deep, not even good enough for 2' deep. I would not even use 1/2" glass.
My thoughts are (using the available calculators in the tank build form) that you would need 3/4" thick glass and in general you double the thickness needed for glass to get a thickness for acrylic, (based on the calculators) so around 1.5" for acrylic.
The available calculators are for rectangle tanks so not sure how to calculate exactly what you need. I am guessing since your viewing window is going to basically have a joint (corner) in it, you should be able to calculate each viewing window as being in a 7'x3'x3' tank and you will be very safe at using the thickness given. I think you could actually calculate the windows as being in a 4'x3'x3' tank but not sure.
If I was going to build a tank of that shape and depth I would use 1.25" acrylic and 1.5" if I really wanted to be safe although I think 1.25" is fine. If I was going with glass, I would not go any thinner than 3/4".
If you are wondering why you need thicker acrylic over glass than I urge you to read more in the tank build section. To give you a quick explanation, you may already know that acrylic is stronger than glass but what many might overlook is the fact that acrylic is far more flexible than glass. So even though the acrylic can handle the forces involved with no problem at the same thickness as the glass, the acrylic will bow out and then you could have some problems. One is the acrylic would be stressed more than it needs to be and you could end up with leaks because of the flexing of the acrylic could ruin your seal around the window.
So 3/4" acrylic is stronger than 3/4" glass but is way to flexible so you have to overcome the flexibility by going thicker and by the calculators you can find here, about twice as thick as what you would need for glass.
With that said, using acrylic is more expensive due to needing suck thick pieces but you get the added comfort than if a kid chucks a marble, metal toy car, baseball or pretty much anything across the room and it hits that viewing window, it will be no problem at all. Might scratch it but it will not let hundreds of gallons of water into your house along with chunks of glass. The glass could also become pretty dangerous with that amount of water pressure and flow behind it if it were to fail.
But I find glass to be less than half the cost of acrylic (when comparing for a specific tank) and far easier to come by. But I would only use acrylic on a tank past about 300g for many reasons.
1. strength
2. clarity
3. light refraction
4. weight
Sorry for the long post, just hope it helps.
I am pretty sure 1/2" acrylic is not good enough for 3' deep, not even good enough for 2' deep. I would not even use 1/2" glass.
My thoughts are (using the available calculators in the tank build form) that you would need 3/4" thick glass and in general you double the thickness needed for glass to get a thickness for acrylic, (based on the calculators) so around 1.5" for acrylic.
The available calculators are for rectangle tanks so not sure how to calculate exactly what you need. I am guessing since your viewing window is going to basically have a joint (corner) in it, you should be able to calculate each viewing window as being in a 7'x3'x3' tank and you will be very safe at using the thickness given. I think you could actually calculate the windows as being in a 4'x3'x3' tank but not sure.
If I was going to build a tank of that shape and depth I would use 1.25" acrylic and 1.5" if I really wanted to be safe although I think 1.25" is fine. If I was going with glass, I would not go any thinner than 3/4".
If you are wondering why you need thicker acrylic over glass than I urge you to read more in the tank build section. To give you a quick explanation, you may already know that acrylic is stronger than glass but what many might overlook is the fact that acrylic is far more flexible than glass. So even though the acrylic can handle the forces involved with no problem at the same thickness as the glass, the acrylic will bow out and then you could have some problems. One is the acrylic would be stressed more than it needs to be and you could end up with leaks because of the flexing of the acrylic could ruin your seal around the window.
So 3/4" acrylic is stronger than 3/4" glass but is way to flexible so you have to overcome the flexibility by going thicker and by the calculators you can find here, about twice as thick as what you would need for glass.
With that said, using acrylic is more expensive due to needing suck thick pieces but you get the added comfort than if a kid chucks a marble, metal toy car, baseball or pretty much anything across the room and it hits that viewing window, it will be no problem at all. Might scratch it but it will not let hundreds of gallons of water into your house along with chunks of glass. The glass could also become pretty dangerous with that amount of water pressure and flow behind it if it were to fail.
But I find glass to be less than half the cost of acrylic (when comparing for a specific tank) and far easier to come by. But I would only use acrylic on a tank past about 300g for many reasons.
1. strength
2. clarity
3. light refraction
4. weight
Sorry for the long post, just hope it helps.
