Do I Need Eggcrate?

[celaeno]

i just got 30 lbs of rocks (bluestone) today and was wondering if i would need eggcrate to prevent my tank bottom from cracking. the cave structure i tend to put into the 30x12x12" tank (20 gallon long) is 18 long x 7 wide x 7" high.

 

[Honeythorn]

Perhaps do so just to be on the safe side?

 

[celaeno]

would it be safer if i put a long rectangular piece of slate to support the two pillars on the right? here's a photo of what i did:

 

[tangokitty]

I didn't know that you can use egg crate in your tank! Your cave looks good.

 

[Dorkhedeos]

If you have sand or graven already in your tank, i wouldnt worry about it too much. Ive seen 60 pounds of rock in less than a sq ft on tanks many times. As long as you have on top of substrate, I think it should be fine.

 

[Honeythorn]

Not so fine if you have fish that like to dig ( like Kribs ) They could undermine the structure if the rocks are loose and sitting on top of the sand/gravel. The last thing you need is for any pieces to topple over and crush fish or go crashing into the glass.

Celaeno - If I were you I'd use blobs of aquarium sealant to "glue" all those rocks together and make them safe. The flat slate under the right hand pillar is a good idea.

 

[OldMan47]

You want to make sure that there are no single contact points applying pressure to the glass. If you can't do that with the rocks or slate then the egg crate plastic is a good idea. It will ditribute the load from the rocks uniformly and avoid giving sharp points of pressure. If you read information about materials strengths and properties, these sharp points of pressure are called stress risers but the concept is easy to understand. It's the reason that a sharp knife cuts easily and the blunt edge of a piece of metal doesn't. The sharpness allows the forces to all concentrate in one place and go right through the object. In this case the object being cut is the tank glass.