Tank safety factor?

[jbdreefs]

You can have an all glass aquarium without the bottom plastic trim, right?

If the stand has a solid top covered in foam, would that not increase my safety factor for the bottom pane? I feel like all the online calculators assume the bottom pane is suspended.

 

[ghbrewer]

Glass tank bottoms should float, not have the front back and sides sitting on top of the bottom pane, IMO. There are tanks you can purchase that do not have the bottom trim. Reef Savvy tanks do not have a bottom trim. You just have to make sure the bottom pane is twice the thickness of the back, front, and sides.

 

[ghbrewer]

Note, when I say float, I just mean the bottom pane is floating in between the other panes, not that it necessarily has to be raised.

 

[jbdreefs]

Help me understand why the floating bottom is more advantageous over the other option? Does it come down to economics? One thicker bottom panel would provide the same surface area for the bond (using the floating configuration) and be cheaper than using the thicker glass for the vertical panes (which would yield the same surface area).

 

[ghbrewer]

The pressure is greatest at the bottom of the tank, so that is where you want the most surface area. Thicker side panes will help to reduce bowing (especially on longer panes), but you need the additional surface area for silicone at the bottom of the tank. Another option is that you can use euro bracing around the bottom, it is just tricky since the silicone in the middle of the brace will never cure.

So, for example, my 100g tank that I built measures 54"x24"19". I built my tank entirely of 1/2" glass with 3.5" wide x 1/2" thick eurobracing. If I were to follow the calculators online, I might have been able to get away with 3/8" sides and 3/4" bottom (accounting for approximately 17.5-18" water depth). Since I already had a lot of 1/2" glass on hand, I decided to go with all 1/2". My bottom is raised approx. 1/8". My tank sits on a 1/4" thick closed cell foam yoga mat. I feel that the eurobracing gives me the additional surface area that I need at the bottom of the tank, but a 3/4" thick bottom would look much nicer if I decide later on to run bare bottom.

 

[ghbrewer]

Had to edit the above post, it was unclear.

 

[jennm]

Not sure I'd want to put foam - if it doesn't crush evenly the tank can twist a bit, and that never ends well with a glass tank.

 

[ghbrewer]

Jenn,

I agree completely when discussing tanks that have bottom trim. When discussing unbraced/trim-less tanks, closed cell foam is considered necessary to prevent point loading on the bottom pane and bottom of side panels. If a grain of sand or other rigid particle were present between the tank and stand and making direct contact with the glass, it could cause a chip or crack. Closed cell foam such as cross-linked polyethylene reduces the chance of such point loading. Closed cell foam is the only type of foam that I would recommend, not the varieties that are seen more often such as what is used in home construction. That kind of foam could very well settle unevenly and cause issues.

 

[jennm]

In that case, IMO going trimless isn't worth the risk.

Jenn

 

[jbdreefs]

I appreciate the conversation.

I just took the bottom trim off a 90 gallon tank and was surprised to see the thickness of the bottom panel. It was half the thickness of the sides... Granted... It is probably tempered and it also has additional support, via the trim, in the middle. It was still surprising.