how to put rocks in my tank

[diver21]

So i didnt know exactly what area to put my question in so i shoved it in here.

i have a tank 1000x 400x 400 and its on a stand which only supports the tank around the edges. base is 6mm glass. and the poly is only on the edges, tank has a thin layer of gravel on the bottom,

question is is i want to pile up some rocks in the tank to serve as hideing places for my convicts, and im worried that they maybe too heavy for the glass and that the points of the stones will cause pressure points on the glass and make bad things happen, realy bad things as theres another tank sitting under this.

so what do i do,

1, add the stones as they will be fine?

2, use driftwood or some other ceramic and lightweight cover instead?

3, add some eggcrate or similar to the bottom of the rocks to spread the load?

4, do nothing

[Adrienne]

If I was you I wouldn't add anything else to increase the weight on the tank base. Are you able to put plywood and polystyrene underneath the whole tank to provide bracing?

Maybe I am being too cautious as initially it may seem okay but it will only take a rock to drop and the base will very likely crack (this is coming from someone who had a 100 litre tank split the other evening and deposit nearly all the water over the shed floor before it was discovered).

Driftwood may be okay if it is light and as it doesn't have sharp edges.

[diver21]

but then ive heard stories of some people in the states swearing black and blue that you should only support a tank by its edges, and not the center as that makes the base more prone to splitting

[Stella]

how wide is the support around the edges?

I have a tank 1200 long x 35 wide x 50 deep, 10mm glass supported around the edges by 7-8cm wood.

Another tank is the same size but lying on its back supported by 2" wide wood around the edges and down the middle.

Both have a LOT of rock and gravel.

I do have undergravel filter plates under the gravel in both tanks, to reduce the point-impact if I drop a rock while moving things.

If you are worried I would recommend putting some wood under. Personally I wouldn't go for ply as it is so bendy, but whatever works for the situation.

[diver21]

3cm on all sides with 20mm thick poly.

tank also has a strip of supporting glass running along the front and another on the back, strip is about 40mm wide. if that helps or not.

[Snowman]

All my tanks have full 20mm marine ply then 20mm poly ranging from 130-800ltrs and ive never had a problem. Would have 130kg of rock in the 5" and 120kg of gravel in the 7". My thought is the easiest way to break something is brace both ends then weight the middle.

[Stella]

Marine ply is often recommended for fish-tank related stuff, but it is designed to be highly flexible, and then be thoroughly fibreglassed. It is not more water-resistant and long lasting like most people think.

Diver, is it a commercial tank and stand arrangement, or a home job? If it is commercial it can probably withstand a lot, if not, I would definitely get something solid underneath before making your rockery.

[jude]

I have always had rocks in my tanks. One tank had a double layer of glass at the bottom but the other large tank only had one layer of glass. I used polystyrene under the tank and another sheet of polystyrene in the tank. The one inside the tank was cut slightly smaller so that it didn't show at the front and sides once the gravel was added.

[diver21]

the stands where part of a quranteen facility, but that would make me think of bare tanks with minimal scaping (havnt seen a quranteen facility before). and i dont thin that if it was a comersial or homemade job would matter too much as the thickness of the bottom payne is still 6mm, or the other tanks are laminated 3mm (2 sheets laminated together)