Warren

A simply supported tank (metal stand supporting only the edges of the tank) requires thicker bottom glass than one with a supporting panel. In saying that, the panel used must be very stiff to have any effect. If only 12-18mm of wood is used it actually has very little effect. The deflection of the glass is quite small even when the glass is near it's maximum tensile strength. Wood bends a lot more than glass. So, the wood needs to be thick enough so it supports the load without deflection. You have 2 options: 1. Use a simple metal stand with a very thick base for the size of the tank - 25mm+ for the tank this size. 2. Add extra metal braces to the stand front to back and left to right to break the area down into smaller rectangles / squares of 200mm or so. Then a thinner wooden spreader can be used. The technique I use for getting a good flat base works for either metal or wooden stands. Sit the stand where it will live but have it minus it's top wooden piece. Spread no more nails or a similar adhesive over the top of the base supports. Fit the top wooden panel. Sit the empty tank on some poly on top of the base before the glue sets. If the glue does not start to ooze a bit then start filling the tank a little. As soon as the glue oozes, stop and take a bit of water out of the tank. Wait for the glue to completely set before fully filling the tank. This means the top wooden support is dead flat to the bottom of the tank and the glue takes up any unevenness in the stand. It almost guarantees even pressure between the bottom glass and base. Using this method you will not have to worry about the weight of the rocks. To stop point loading of the rocks you propose to put into the tank, you can add a little gravel to the bottom of the tank. This will help spread the load a bit and stop a single point touching the glass. If you don't want to use gravel then silicone will do a similar job. Squirt a bit of silicone where the rock will sit. Place the rock into the silicone. It will still be touching the glass at this time. Put a enough small packers under the rock to lift it a few mm above the glass. Once the silicone has completely set you can add the rest of the rocks. Alternatively a bit of medium hard rubber will do a similar job. The target is to stop a single sharp point touching the glass. A common misconception is polystyrene takes up unevenness in a tank base. It will only stop point loading (eg, grit or a screw head) but will do little to nothing to help with a tank base than is not flat (eg, has a hollow or twist). In most commonly sized aquariums the surface loading on the poly is not enough for it to deform and take up the load. If it did, it would squash flat over a very short period of time. It will help with some of the high points a little but will also stress load the bottom glass panel of the tank at the same time. Get your tank base as flat as possible.

Hadn't noticed this, - is now fixed. Maybe when things like this are noticed in the future people could be kind and proactive enough to let us know...

We do get most of these plants and fish already. NZ native freshwater shrimp adapts reasonably well to tropical temperatures if collected from warm streams in summer. Most people just don't learn enough and put in the effort to have a tank that looks this good is all.

Allowing for glass thickness, 6mm glass = 80.92L to the top 5mm glass = 81.86L to the top If not filled to the top, subtract 6mm glass -0.216L per mm from the top 5mm glass -0.218L per mm from the top

I currently have an 8' tank (2400L x 820W x 660H) and approx 1200L. It's a bit of a mission to move and I've had to do it twice. Hopefully only 1 more time max... The tank weighs approx 330kg and the stand is about 400kg. There's 600kg of gravel in it. It really hurts to take this amount of gravel out and put it back in the same day and you feel really broken afterwards... I used to have a 3000L x 1000W x 1200H (front viewing window of 950) (external dimensions) and the bottom at about 1100 deep so the gravel came up to the bottom edge of the glass window. Was approx 2940L. This was a real mission to move and required a crane as just the tank was 750kg empty. The first time I had to move, I sold it as it was too much of a mission to move this, the 8', 2 x 6' and a 900mm diameter cylinder tank as well as the other 36 tanks in the garage. It was a real shame as I only had it set up for about 2 months. It did add $120 to my power bill (and that was 6-7 years ago so it would cost a lot more now). I once looked at building a 32000L tank (7.5m x 2.4m x 1.8m) down the side of the house to become the lounge wall. The cost to build wasn't too bad at approx $12K. However the cost to run it would have been at least $750 just in power so that killed it before I even started. A tank this size is only available to the wealthy or someone willing to put the time and effort into using natural resource to power the tank (wind, sun etc). Most people don't realise an aquarium uses it's purchase value about even 18 months to 3 years depending on how good the deal was.

If you try DIY yeast CO2, put an empty catch bottle between the generator bottle and the tank. All the yeast sludge will get caught in this bottle...

Hi Barrie, It's not two sets of data from the same supplier. My data is what I worked out myself with guideline information from Pilkingtons and from their glass datasheets. There was nobody at Pilkingtons NZ or Australia who could (or would) do the maths involved with the calculation of glass thickness for aquariums - didn't go further than this though (I'm sure someone there in another country knows how to do it). What I've come up with gives very similar results to the Pilkingtons tables for glass thickness for aquariums. What it does over what the Pilkington tables is tells you the exact thickness required for a tank of given dimensions and can mean a glass thickness less or more + it covers dimensions outside their table. The Pilkington table gives bands that could mean glass thicker than required gets used - increasing cost. You sure are right about the passion for what you do. It means the difference between a good job and something else...

Yes, cut them about half way down. Most of the bottom parts will branch into two new ones so you'll end up with twice as many. The trick with stem plants is to remove the whole plant when it gets too tall, cut off the bottom part and replant the top. Then you always have the new fresh growth looking it's best. I use the method all the time and replant the bottom part where it can't bee seen if I need more plants.

Ramset have (or had) a black silicone. I used it on my old 3m tank. It's now 6 years old and still going strong. Std acetic cure.

The engineer who designs the aquariums and wrote the guides and charts glass merchants use... I have contacted Pilkingtons and that's where the 3.8 comes from along with many other aspects for how the calculations were derived. I think there's skope here for properly engineered aquariums and experience. A good glass merchant with the appropriate knowledge and experience is key to a good aquarium design. There are only a handful of these people in NZ however and most of them have been mentioned on this website.

Yes, you can make a tank to a safety factor of 1.00 if you want and it might hold the water - just don't bump it. The safety factor of 3.8 come from years of statistical analysis on building aquariums and the typical purity of glass. It allows for the common defects found in the glass during manufacture and the general wear and tear an aquarium is likely to see during it's life. Obviously it cannot cover every situation. However, a safety factor of 3.8 means an aquarium if designed using the correct methods and using the correct glass thickness will have less than 0.1% chance of failure over a 10 year period.

What ark?

Your tank's front and back glass has a safety factor of 1.75 (or 175% of the breaking strain of the glass). While this is a long way off the recommended 3.8 there are many tanks with similar loadings out there. They usually survive for years but obviously do not have as much tolerance for movement (eg earthquake) as a tank designed to the recommended minimum. To meet the 3.8 safety factor your tank should have 15mm front and back glass, 10mm side glass and 12mm bottom glass.

Are you any good at calculus?? Do the research and maths and you'll find I'm correct. The glass thickness article is based on common engineering practices and recommendations from Pilkingtons. I think they have the experience to make a safety factor recommendation. There is no black-art, how do you think buildings or bridges are designed - trial and error?? Calculation is the cost effective way to make sure you do not over design while making sure you meet a statistically safe safety factor. It's all standard engineering practice - trust the maths. If you cannot, then you'll never enter a tall building or cross a bridge again. To question designing aquariums by calculation but not bridges or buildings baffles me - maybe I've been an engineer too long... As I stated earlier, there are very few glass merchants who know anything about designing aquariums... However, if you find someone with good experience go with them as they'll be your best best. DIY without proper knowledge is a potential disaster waiting to happen.

Most don't know and have little or no experience with aquariums. Use the calculator in the link above with a safety factor of 3.8 then you know for sure. You can't beat the maths behind it...

Read this, it will answer all your questions about glass thickness for aquariums... Read it thoroughly though. http://www.fnzas.org.nz/articles/techni ... _complete/

A bit on lighting but not much on plants. When set up properly, you'd only need a few plants for most of these tanks. In about 6 weeks you'll have grown enough to fill the whole tank saving a lot on buying everything up front. Then every two weeks you'll be able to sell about 1/3 of the tanks plants and recover the cost of the lights within 6 months...

Thanks but go for safety factor of 3.8 or more if you can...

Rotala macrandra grows like a weed and is quite red if the lighting is strong enough and you feed it enough iron.

They are hungry and want the food. When I kept Oscars, they did this all the time. It's also a good way to get the food before any other fish does - survival of the fittest. In the wild, most fish will jump out of the water to catch bugs or friut growing on trees overhanging the water. Was a good party trick...

Yeah, any sharp point will do it... The only way to stop absolute disaster is to laminate 2 or more panes together with each pane being able to support the full load. Then if a point load cracks the outside pane the inner pane(s) will hold. There's very little that can be done to stop the law of natural selection however...

The difference here is you are applying your weight to a single point instead of evenly distributing it over a large area. With fluid dynamics, even though there is a large weight, it does not necessarily mean large forces on the glass - it all depends on shape. Also, the recommended safety factor for tanks of 3.8 allows for unequal stress and weak points in the glass. Statistically, tanks built using the calculator to a safety factor of 3.8 and properly supported will have less than 0.1% chance glass of failure over their life. They will also easily cope with being knocked, even by 105kg... The problem with most tanks available from pet shops or built by hobbyists on gut-feel (or past got away with it's) is the safety factor is less than 2. In this situation knocks can easily cause failure. To give you a good example, I built a 3m x 1m x 1.2m tank, fibreglass over plywood in a 75mm square steel frame. The front glass was 950mm tall, 19mm thick. When full, I kicked the front glass as hard as I could in my tramping boots to check it could withstand a decent knock. The calculator said it would survive and it did. Maths really does work, it's how all well engineered things are designed. Get the maths right and the product is perfect...

The glass thickness calculator assumes Euro bracing is used.

Go to the clubs pages off our homepage: http://www.fnzas.org.nz/clubs/western_b ... d_society/

I'm sure Wok would love to take up the challenge ron