Warren

Notice the link in the image: http://www.fnzas.org.nz/?p=1732 The calculations come from my article on the FNZAS website. If you read the article it tells you everything you need to know about how to work this out for yourself. Toughened glass has a tensile strength of 175MPa vs worst case 19.3MPa for standard float glass. All you need to do is change the tensile strength in the calculations and it will tell you glass thickness is required. For a window 3000mm x 900mm you only need 7.65mm toughened glass to achieve a safety factor of 3.8. On a tank this size I wouldn't consider for a second going below 3.8 safety factor... The deflection on the glass will be 12.79mm but it will hold. If you took the 19mm panel you were considering and toughened it you would get a safety factor of 23.42 so somewhere in between would be fine.

It depends how strong the base really is. A 400L tank will likely be around 600kg with everything set up and full to the top. The bottom glass and base will share this load. What you need to do is calculate the deflection of the bottom glass as if it had no support from the base. In this case you will need 17.46mm glass and it will have a deflection of 0.29mm for a safety factor of 3.8. As long as the center area of your stand has less than 0.29mm deflection with 600kg evenly distributed on it, it will help to support the weight of the tank with some relatively complex ratio depending on many factors. If the stand has more than 0.29mm deflection then it will have very little effect on the force on the bottom glass and the ratio of support from the glass to tank will diminish very rapidly. It's very difficult to build a base that's rigid enough to support all the weight with no deflection and well braced steel is your best friend here...

Most often acrylic needs to be annealed after being cut to releave / equalise the cutting stress. The bigger and thicker the sheet the more important this is to do. The process involves heating the cut sheets to the annealing temperature in an oven for several hours and then cooling slowly (don't ask me what the temperature is or exactly how long - the duration probably changes for sheet size and thickness). If this is not done the Acrifix will effectively stress releave the edge only and can cause fracturing. This is especially important if you've drilled holes...

Did the shop actually sell this as an aquarium or something else - maybe it's meant for plants...

I think you should read my article about glass thickness before you consider filling this tank again. You can find it here: http://www.fnzas.org.nz/?p=1732 This link will take you to a tool for calculating the safety factor on an aquarium (also at the bottom of the page): http://www.fnzas.org.nz/?page_id=1529 When filled to the top this tank only has a safety factor of 0.742 which means it should break. The reason it didn't is possibly because you have glass on the higher end of the tensile strength range or maybe the 10mm plates helped somehow. Unfortunately, the builder of this tank like many other tank builders, has no idea how to work of the required thickness to make a safe tank. You can use the tool in the second link above to approximate how much you can fill the tank to get a safety factor you are happy with. I'd go for 2.5 minimum but recommend the commercial standard value of 3.8 as a better target. Safety Factor 2.5 = 421mm (approx water height) Safety Factor 3.8 = 366mm (approx water height)

Yeah these guys plagiarised my glass thickness article and calculator and didn't bother to give any credit!!!! :evil: :evil:

Any sheet of wood you put under the tank will do almost nothing to distribute the weight. The glass deflection on the thickness you're planning will be minimal. If you put the same force distributed on 20mm of flat wood panel it will deflect much more than the glass therefore will supply no extra supporting strength. I wouldn't trust most of the stands I've seen in a fish shop. They're often made without any stress calculation and will collapse in an earthquake easily. If it's a steel frame then most of the force will be taken up by the tank with the highest pressure points where the legs join the rest of the frame. Unless the steel members directly under the tank are very wide they will also deflect more than than the glass and not support nearly as much of the tank as you might think. If you were to use 150 x 50 x 6 RHS under the tank and support that with a leg every 600mm then the steel will give good support as there will be almost no deflection between the legs.

I think you should do the research - it's not that difficult. Then you will find the permit costs are very high. You will also find that each individual food type also has to be registered. The cost gets very high very quickly. There's no need to split as the people who need to know are mostly reading this thread. There will be further information added to the site shortly to help.

The point everyone is missing here in their stampeeded rush to try to expose Hollywood's as ripping everyone off is this; When importing for personal use you do not have to pay the fees to the required authorities for the permits and tests to legally resell an imported food item. These fees are considerable and given New Zealands tiny population and tiny market these fees add significantly to the retail price. If you want to import food for personal use fine, do it. You just can't on-sell anything you've imported to anyone else without the same testing and permits Hollywood's (or any other importer) has. Before you continue to complain about the price of anything in any retail shop you really should be fully informed about all the costs involved in the industry before pointing the finger at anyone for profiteering. If you can actually prove they're profiteering then by all means let us know. However, if you are just assuming you are being ripped off because you don't like the price then don't slate the retailer until you've done your research. When you add in all the costs you'll find the price is actually very fair. This has nothing at all to do with Hollywoods specifically, it has 100% to do with the regulations anyone who wants to resell food products it NZ has to comply with whether private or a business. May I suggest in the future people who want to complain about any price do their research first. You should also find out if you are allowed to sell something before advertising it on this website (or any other website) or giving information to others about where to buy it. It's your responsibility to know and you need to check the regulations before you do it. Saying you didn't know will not help you when the authorities come knocking at your door - just like fishing quotas, it's your responsibility to know what your size limits and daily fish counts are (MAF won't care if you didn't check)...

Yipee, I just checked my server and I still have the finished tank photos and CAD files from the design/build so doing an article suddenly gets much easier... Yeah, yeah :smot: sorry (but interesting though).

Hi David, no I never did do an article but did describe the process in lesser detail in a post ages ago. I don't even know if I still have any photo's... However, it would be interesting to write up so I could do something for the AW and post it up here after that.

I once used the professional type to lift my old 8' tank. Empty it was around 300kg and just too difficult to lift from underneath. We used 6 x 200mm diameter suckers which stuck on no problem. The tank will definitely not pull apart when being lifted this way as the force to lift the empty tank is only a fraction of the force on the silicone joints when full of water... I feel this method is much safer as you have a nice handle to grip instead of you hand curved around the sharp glass edge where it's easy to slip off. The type of sucker shown in the photo above would really only be any good for small tanks as you don't get anywhere as good a vacuum. If it's big you want the professional type with a pump-button to create a really strong vacuum between the sucker and the glass. To me 5ft 500L is smallish. My tank was 1200L 8' and I considered it medium sized. The 3000L tank I made was approaching large but that needed a crane... 8) In saying that, using glass suckers on any tank really makes life much easier as you have a very firm place to get grip vs a sharp slippery glass edge.

You could use both. Roughly stuff the gaps with chunks of poly and fill the gaps with wool. Then you use up all the spare poly and get to use wool as well - bonus!!

Past quiz nights have proven very popular - probably because they're very enjoyable and a good laugh. All welcome, see you there!!!

Got mine today. I think this has to be the best AW ever made - there's something about it that really stands out. Well done Caryl, superb job!!

Actually as one of the creators of the rules (many years ago when the site began), the bulk purchase rule was specifically aimed at people doing direct/parallel importing who were looking to get enough to buy a minimum quantity. If a group was organised to make a purchase through the proper channels (either through a retailer or friendly importer) there should be no problem - except the site rules still don't really allow it. As I said, the rule is to stop direct importing of things like food, filters etc. I will ask the moderators to consider an alteration to the rules to allow organising bulk purchases through the retail channel for standard products and wholesalers for specialised products (only if retailers are not interested in helping). I won't guarantee success as it will go to a vote but I will try... And to address another question about using the PM system to do it - the rules state that all rules also apply to PM's...

I looked at this problem when I had tanks too. There seems to be very little available that isn't very expensive. You can buy industrial controllers with the temperature accuracy you're looking for which also include PID control to help keep the temperature even more stable. I currently have no fish (shame I know) but do have a controlled server room. I wanted to keep the temperature at a constant 25'C±0.5'C and humidity at 50%±2%. This was going to be possible with industrial controllers but at approx $2k for the parts I decided to make my own. I purchased an accurate humidity sensor and borrowed a high accuracy temperature sensor from work permanently (could have bought one for $1.50)... Then I designed a controller using an Atmel AtMega16 Microcontroller + 20 x 4 Character LCD Display and made up a small PCB to put all the bits on. This switched a series of relays to control heating, cooling and humidity and speed controlled fans. Writing the C code was the funnest part as I'd never written code for PID control before so there was a big learning curve. I could have just gone with proportional control only but that would have meant accepting variations in actual temperature vs setpoint temperature due to the amount of energy required to control the temperature. Are you interested in making your own - then you can still spend money and build something

PHP5.2.x - PHP5.3.6. There are a few compatibility issues with some of the mods applied to the site. The code for the site has been very well written and tested and probably worked fine. We went straight to the latest version to be sure though before pushing the files back to the live server.

My understanding is it changes very little. You can be sure by finding the datasheet for the different types of glass and comparing the tensile strength. They should only be a very small percent different if any.

Yes, the power bill has increased a lot over the years I kept fish. It seems to be increasing faster than inflation. 8)

You're welcome. I'm sorry it took so long due to being away overseas.

At 500mm tall and 10mm glass you will have a safety factor of approx 3.5

Here's the results: [table][tr][td]Safety Factor[/td][td]Thickness[/td][td]Deflection[/td][/tr][tr][td]2[/td][td]9.95mm[/td][td]4.76mm[/td][/tr][tr][td]2.5[/td][td]11.2mm[/td][td]3.41mm[/td][/tr][tr][td]3[/td][td]12.19mm[/td][td]2.59mm[/td][/tr][tr][td]3.5[/td][td]13.16mm[/td][td]2.06mm[/td][/tr][tr][td]3.8[/td][td]13.71mm[/td][td]1.82mm[/td][/tr][/table] 12mm Glass will give a safety factor of 2.91 - it's up to you to decide if this is enough...

You can calculate the actual thickness of the glass by replacing the apha and beta constants with the ones below which modify the glass thickness calculator for the top edge of the glass unsupported. [table][tr][td]a/b[/td][td]beta[/td][td]alpha[/td][/tr][tr][td]0.5[/td][td]0.08[/td][td]0.0036[/td][/tr][tr][td]0.667[/td][td]0.1246[/td][td]0.0099[/td][/tr][tr][td]1[/td][td]0.2[/td][td]0.04[/td][/tr][tr][td]1.5[/td][td]0.36[/td][td]0.167[/td][/tr][tr][td]2[/td][td]0.44[/td][td]0.416[/td][/tr][/table]

Pressure is proportional the the height of water. In this case it's the height of the water in the tank to the height of the filter. Get enough height between the tank water level and the filter and it will burst. If the filter is below the tank it will have pressure in it. If it's above the tank it will have negative pressure as long as both pipes are under water. If one is above the water and it's turned off, all the water in the filter and pipes will siphon back into the tank. If you don't believe me just get a hose and create a siphon out of your tank. If you lower the end of the hose the pressure on you finger get higher - just try it (it's only physics)...