David R Posted August 25, 2004 Report Share Posted August 25, 2004 On sunday the base of my 4'x15"x15" tank cracked. I brought the tank second hand and had it set up for about a week. I had a lot of big rocks in the tank (was set up as a rift lake cichlid tank), and initially thought that was the reason for the break. Talking to Brian at the goldfish bowl today, he said it was more likely my stand may not have been level and that was more likely the cause of the crack. I'm having the tank repaired, and I'm wondering what thickness glass to use for the bace? I was thinking about going for 10mm (the rest of the tank is 6mm) as there will be a lot of rocks in the tank. If it was the stand that caused the crack then 10mm wont be necessary. Is 10mm over-kill, or would it be better to over-engineer?? Quote Link to comment Share on other sites More sharing options...
Caryl Posted August 25, 2004 Report Share Posted August 25, 2004 Always better to over-engineer. Warren is the expert on this but I would not be happy with a tank that size using less than 10mm glass. Both my tanks (similar size) are 10mm. I think pegasus said he has had a 6mm last for years though. Most important is to make sure whatever the tank is sitting on is level. It takes very little (maybe even a small bit of dirt) to cause a stress fracture. Was it also sitting on polystyrene? Quote Link to comment Share on other sites More sharing options...
David R Posted August 25, 2004 Author Report Share Posted August 25, 2004 Yup it was on polystyrene. Quote Link to comment Share on other sites More sharing options...
Rob Posted August 25, 2004 Report Share Posted August 25, 2004 I'd probably opt for the 10mm - don't want any repeats. I'd also have polystyrene in the tank underneath the larger rocks to minimise any point contacts from the rocks - then the polystyrene can be covered up with gravel. Also it's often recommended to place the stones directly on the base (with the polystrene I like to use) rather than on top of the gravel - as fish often like to shift gravel - which will then destablise the rock structure. Quote Link to comment Share on other sites More sharing options...
chimera Posted August 25, 2004 Report Share Posted August 25, 2004 i would also go 10mm, my current 4 footer is 10mm and its sweet. also consider, if you think your stand is not 100% level and you have no way of fixing it, to use a double thickness of polystyrene under the tank. i have some 15mm poly when my 5 footer goes in this weekend but I am seriously considering going 20mm - 30mm instead. With the extra weight of the rocks it will take up those extra deviations you may have in the stand. Quote Link to comment Share on other sites More sharing options...
David R Posted August 25, 2004 Author Report Share Posted August 25, 2004 The rocks were placed directly on the base of the tank, and there was only a small layer of gravel added after that. The stand was 12mm custom wood sitting on concrete blocks, with one at each end of the tank and one in the middle (kinda like this | -- | ) so it may have been that the wood had a slight twist in it. I'm going to get an engineer to weld up a steel stand this time. Quote Link to comment Share on other sites More sharing options...
chimera Posted August 25, 2004 Report Share Posted August 25, 2004 my 5 footer will be sitting on 12mm ply over a timber frame. i have 3 x 3x2's running along the length of the tank, one on each side and one straight down the middle. all lengths are furthur supported crossways by 4 x 3x2's - giving it 8 legs. I think timber is sufficient so long as no cross section is able to bow and its reinforced where ever reinforcing it needed! My entire stand sits on another stand that is nailed to the floor. This stand has 6x2's laid flat along the floor (to disperse the weight evenly across the floor joists) with a large amount of timber in cross sections - feels as strong as a concrete slab but without the massive weight I estimate with the tank, stand, water and all the live rock, it will be in excess of 1 ton. Quote Link to comment Share on other sites More sharing options...
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