Building your own fish tanks - Guide & Forum
By Tim Gautrey
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This guide is suitable for making any rectangular or square glass fish tank. It is not suited to shaped tank construction.
When I build my tanks, I always use clear float glass and have it cut to the correct size, the edges of the glass should also be bevelled so that there are no sharp edges but rounded edges. The size of the tank determines the thickness of glass required. Depending on the water volume that the tank will contain you will need 4mm, 6mm or 10mm glass. I always use either 6mm or 10mm for the bottom of the tank, as this is what takes all the weight.
The rule of thumb that I use for this is tanks that are less than 15" (381mm), 4mm is sufficient, less than 18" (457mm), 6mm above 18 (457mm)" and below 36" (914mm) 10mm. Any higher than 36", talk to the glass supplier, because you will need very heavy panels and it may be best to leave larger tanks to specialist tank builders! The length or front to back depth of the tank doesn’t affect this calculation, as the cross-stress bars come into effect. Don’t be tempted to cut the cost by reducing the thickness of the side panels, it’s not worth the risk!
Calculate the sizes as follows to give maximum strength on the joints
Bottom: Full length x full depth, (front to back), for the overall size of the finished tank.
Front and back panels: Full width and full height minus thickness of the bottom.
Side panels: Full height minus thickness of bottom, depth minus thickness of front and back combined.
Stress bars: Full length minus 50mm x 50mm wide from same thickness as front and back; the length of these should be the distance between the front and back panels. The stress bars should be placed at an even distance from the sides of the tank and run from the back glass to the front glass.
This will enable easy construction too, as everything sits on the bottom panel.
To construct, follow the procedure below
Prepare a flat level surface to work on. This must be clean and free from dust and grit. When assembling the tank, you will almost certainly get silicon on this surface, so make sure that it can be cleaned off afterwards or discarded. (Don’t use a kitchen table unless it’s laminated. The glass will dig into the timber or veneer and ruin it!)
Methylated spirit should be used on all jointing surfaces to remove any traces of grease or dust before silicon is applied. This is very important. Any grease on the jointing surfaces could lead to leaks sooner of later. Make sure that the jointing surfaces are completely dry before using any silicon on them.
All edges should be polished with emery to round them off for safety. This can be done before or more commonly after assembly.
The silicon should be aquarium safe silicon, i.e. no fungicides added. Run a bead of silicon approximately 6mm thick along the edge of the panel where you want to join. Press the join firmly together to squeeze the air out and then tape in several places on the outside edge with decorators tape to hold the join together while the silicon cures. Run a second bead down the inside of the join and round off with a spoon handle or finger. If you are not well practiced with this, use masking tape on the glass either side of the bead to ensure a nice straight edge. You will need some help when you start the assembly, as the first couple of joins are very unstable.
Start with the back panel to bottom. I always lay the back panel on the work surface and bring the bottom to it. This ensures that the edge of the glass is flush with the back panel. Press the join together firmly and tape it up. Then the two side panels are next. Silicon bead the edges and press the joins together firmly and tape. This will stabilize the construction and it will be easier once these four panels are together. Don’t forget to internally bead the joins, as this becomes more difficult after the curing starts. Lastly the front panel can be fitted. Let the silicon cure for an hour before attempting the next stage.
Stress bars can then be located 25mm from the top of the front and back panels, running horizontally and centrally placed. Run a bead of silicon above and below the stress bar to ensure that it stays in place. Let this silicon cure slightly before fitting the cross stress bars. The cross-stress bars should be secured from front to back on the top of the stress bars, making sure that you leave a gap at each end for wiring and tube access. Don’t be sparing with the silicon here. Make sure that when the cross bars are pressed down onto the stress bars, there is enough silicon to completely seal the join, or it will look unsightly afterwards.
If you get any silicon on the glass where it shouldn’t be, don’t worry. Wait for an hour or so, then scrape it off with a sharp blade, and wipe over with methylated spirits.
That should cover the basics. Follow this guide and you will never fail to make a waterproof tank every time.