Warren

Toughened glass has just over 5 times the tensile strength of standard float glass (on average). If you take the same panel and toughen it the safety factor on an aquarium will be significantly higher requiring much more force to break the glass. You can substitute the tensile strength of toughened glass into my glass thickness calculators to see how much extra safety factor you will get. I wouldn't recommend using toughened glass to decrease required thickness, only to improve safety factor. If however you use toughened glass you must also accept its failure mode compared to standard float glass. Typically float glass will crack and water will leak out slowly where toughen glass with utterly shatter like old car windscreens and all the water will burst out at once. I suppose at least it gets it over with quickly... 8) My next tank will use 15mm toughened low iron glass which will end up with a safety factor of just over 22, well above the 3.8 recommended for a good statistical chance of no problems. This is due to the serious earthquake risk in Napier. With a safety factor of 22 it's unlikely the glass will break even if the house falls on it.

Ira is 100% correct. The only thing that matters is the pressure difference between the inlet and outlet. Since both are more or less at the lame level the energy required to move the water is exactly the same irrespective of how far the filter is below the water level. You could even take the filter above the water level once it's running at it would still work and use exactly the same energy. Go research the laws of physics and it will all become clear... The only thing that changes by moving the filter height is the pressure inside the filter. lets just put this one to bed :roll:

Check the size and litres rating of the pre-filters. Add the filtered water per day + permeate waste together as this will be the total water going through the prefilters. It will give you some idea how long they will last. Check what they cost to replace and you'll get some idea of the running cost. Membranes last for a very long time if you have good quality prefilters. Some of the cheap units used specialised pre and post filters and because they're proprietary they cost an arm and a leg to replace... I ended up replacing my pre and post filters with standard readily available units with a much larger capacity and it lowered the running costs to approx 25% of the proprietary parts. It also gave me a much better selection of filters to use. As long as the unit already has standard filter housings it will be cheap to run.

Yup, and and a properly shaped tube sticking down into the pump flow outlet will do exactly this...

+1 Must have a poorly designed venturi (or none at all). Most pumps just have a hole and call it a venturi... It needs a properly shaped tube sticking down into the pump flow outlet to be called a venturi. Got a photo of it?

It sounds like the stand is deflecting with the weight of the water in the tank. If this is the case the gap will get bigger as you fill the tank more. The poly will not take up the gap as it does not squash more than a fraction of a millimeter. Poly is intended to only take up point loads like grit or screw heads sticking up a little. The force on the poly is approx (0.001 x height in mm) grams per mm². In your case your tank is 450mm tall so you have .45g/mm² (not allowing for the weight of the tank) - not enough to deform the poly. Another way to look at it is like this - if the force on the poly is enough to take up gaps of a large area then it will end up squashing it nearly flat (like when you stand on poly). Another way to calculate it is: Tank 1200 x 450 x 450 = approx 50kg empty Volume = 243L (approx) so the water weighs 243kg Total = 293kg 293kg / (1200 x 450 for the base) = 0.0005426kg / mm² = 0.54g / mm² (the difference to above is the weight of the glass added in). It will not be a problem if the bottom glass of the tank is strong enough to take the full weight of the water. You will need to strengthen the stand if you want it to stay perfectly flat and take the weight of the water so the bottom glass has little to no weight or deflection. The top of the stand will have to have little to no deflection with the full weight of the tank on it. Any deflection means force on the glass. Alternatively you can share the force on the glass with the top of the stand if you calculate the bottom glass deflection with a full tank and make a stand to deflect half this amount with the full weight of the tank on it.

A few years ago I built a medium sized tank a little bigger than this. It was 3000mm long, 1000mm wide and 1200mm tall with a 950mm viewing window. The bottom 200mm was just the base so the internal height was actually only 1000mm. This meant the gravel level was at the bottom of the glass. It was made from 75 x 75 x 6 RHS steel for the corner uprights, 200 x 100 x 6 RHS for the base and 100 x 50 x 6 RHS for the top rim. 25 x 10 flat was welded flush with the edge of the RHS to form a lip for 38mm plywood for the sides, bottom and back of the tank. This was made by gluing 2 x 19mm building ply together. The ply was held into the steel frame with no-more-nails and a few screws. The base also had several front to back 75 x 75 x 6 RHS supports so the plywood bottom was well supported. This then had 2 layers of chop-strand fiberglass + polyester resin (epoxy is not waterproof). It was finished off with a matte black gel-coat suitable for polyester resins. The front glass was 19mm and was the single biggest cost at exactly $1000 inc GST. This was a special deal from a local glass shop who happened to have a suitably sized offcut of 19mm glass left over from the Napier Airport upgrade. All the steel came from the local scrap metal merchant and a mate and cost less than $100 The plywood came from some crates we got delivered to work so $0. The fiberglass was done by a mate for $400 including materials. The paint for the steel frame cost $75 The silicone glue primer and silicone for the front glass cost $240 All up including a few extras not listed here the total build cost was approx $2000 for a 3000L tank. It was also seismically rated for a pretty big quake - important for Napier...

My glass thickness calculator on this website assumes good perimeter bracing around the entire top (all 4 sides supported) - commonly referred to as euro bracing. This also has the added advantage of reducing twisting of the top of the tank during earthquakes. With 10mm glass you won't need bracing at the top of the tank for it to be strong enough under normal conditions. It will only be required for unusual conditions.

The tank you were looking at of 900 x 450 x 400 has the following safety factors; 6mm - 2.37 (too low) 8mm - 4.21 (good) 10mm - 6.58 (excellent) It's clear 10mm is very thick for this sized tank and gives much higher than the 3.8 minimum recommended safety factor. If 8mm is available and cheaper than 10mm I'd go for that but as Spoon has said - 10mm might be cheaper... Many tanks this size are made from 6mm glass and last a long time. Chances are under normal situations the tank would never cause a problem. In unusual situations like earthquakes it may let go. Another advantage of 10mm glass is nearly twice the width of the silicone join which will give more than 2x the strength of a 6mm join.

I once worked out how to calculate glass thickness and this took weeks to research and understand. So, I certainly wasn't going to try to figure out the stand calculations. I got a structural engineer to do it. It cost nearly $1k but was worth it to be sure. Too many people skimp where it's important spending only a few hundred dollars on the tank and stand and put thousands of dollars of fish in the tank. Then they get all teary-eyed when the tank or stand breaks and they lose all the fish... Think of $$$ spent in the right place as better than insurance.

There's 2 approaches to making things earthquake proof. 1. Let the stand flex so the ground moves but the tank stays relatively still. 2. Make it rigid as and bolt it down so everything moves with the ground. The problem with 1 is if the stand reaches the limit of its elasticity if will fatigue and break. The problem with 2 is everything including the tank has to be designed much stronger. I personally prefer 2 as you can work with absolute numbers and there's no guesswork in the design. It also means it doesn't matter what form the quake takes (single-direction/multi-direction) it will still survive. Of course, you still have to design to a given maximum - the number of G's the unit can handle... I Hawkes Bay I designed my stand for 1G. Given the tank and stand weighed about 2500kg it meant the point where the stand touched the floor had to cope with as much as 25kN in a big earthquake. On top of that you have to allow for vertical motion and guess at how much wave flexing will be in the floor. In the end I went for a stand that could peak at 50kN across 2 diagonal points. This said, I was never happy the tank would hold together even after reinforcing it. If you want your tank to survive big earthquakes you'll need to allow plenty of safety factor into the glass design and use better than the normal but-joint silicone construction method. A safety factor of 3.8 on the glass should do it. Provided no twisting force is applied to the base of the tank glass, double-butted silicone joints should hold together in most big earthquakes. If the stand is not rigid enough, twisting forces will also appear in the silicone joints creating unknown stresses that are difficult to calculate. They also seriously reduce the strength of the butt-joint and create extra stress in the glass. I now prefer steel frame tanks with the glass sitting inside the frame with the silicone joint under compression. My last tank design had a safety factor of 22 - yes, a little overboard but at least it would still be standing after the house fell down around it...

AH, but a tank with the right sized glass and correct bracing with a safety factor of 3.8 will survive the shaky-thing - unless it falls off its stand, gets hit by something else or isn't properly glued together...

Before leaping into UV, you need to identify what caused the fish to die. Was there any sign of disease or did the fish just die for no apparent reason? If the tank isn't properly cycled it might not be disease and UV will do nothing to help...

Make sure you get something with big and 'standard' pre-filters and post-filters. I purchased a unit with specialised filter that only lasted about 3 months with constant use. I ended up buying new standard screw-type water filter canisters that fit standard filter elements. These only cost 2 x the price of the specialised units and lasted just over 1 year. I went with a 20 micron pre-filter followed by a 0.5 micron silver activated carbon pre-filter then into the RO. I didn't use a post filter. The better you pre-filter the incoming water the longer the membrane will last. Check your water chemistry as well - there are different types of RO membranes to cope with specific types of water chemistry. Using the correct type is crucial if you want it to last. Unfortunately you can't get what I was using any more.

Unfortunately the pressure in a CO2 bottle is not a good measure of how full it is. When CO2 is compressed it sits at the bottom of the bottle as a liquid and has a gas layer above the liquid. Until all the liquid phase of the CO2 is gone (basically empty) the pressure stays fairly steady at 1000psi and then very quickly drops at the end when only gas is left. You either have a leak or partial fill. My 6.8kg would last about 8-9 months.

Another very important factor most people completely overlook when buying a pump is the flow curve - this shows the flow at a given head of water. A higher wattage pump for the same flow rating at 0m head will usually pump considerably more water at 1m head than a lower wattage pump. It depends completely on the back-pressure the pump was designed to operate into. Only canister filters operate at 0m head. Sumps always operate with reasonable head (this is the distance from the water level in the sump to the point where the water exits (or to the waterlevel in the tank if the exit is under water). It's very important to check this as the flow could be less than half the 0m head flow in some cheaper pumps. It's likely the cheaper generic pumps you've mentioned are not made to the same fine tolerance as the better quality ones. The air-gap between the motor iron-core and the impeller rotor effects the efficiency heaps. If there's a really big gap between the rotor and wall of the pump it will use more power all other factors being the same. Basically if it looks like it's really well made it will likely be more efficient.

Jaycars specs are wrong - it's not 14W. At 23 cfm it's only 1.4W - also confirmed by the current of 100mA (12V x 0.1A = 1.2W - close). However, at 2800RPM (if this is acurate) it might be a bit noisy. If it is you have 2 options - get a lower voltage PSU or add a series resistor. Every 10 Ohms will give you about 1V drop @ 100mA. Heat loss in the resistor is propotional to V² so there's 4 x the heat for double the voltage drop. eg: 1V drop (10ohms) = 100mW, 2V drop (20 ohms) = 400mW, 3V drop (30 Ohms) = 900mW, 4V drop (40 ohms) = 1.6W etc. If you use the resistor voltage drop method you will need to size the resistor correctly. Pick a resistor wattage about 3x the power loss. Resistors run at about 200'C+ at their rated wattage. Derating to 1/3 means they operate at a sensible temperature instead. eg, 4V drop (40 ohms - use 39 ohms as it's a standard size) = 1.6W so use a 5W resistor... 23cfm is heaps for your application and you will only need a fraction of this.

If it's a 12V fan you could also leave it running all the time but power it of 5-6V. All you will need is a very small airflow to stop the damp. This has the added bonus of making the fan almost silent. A cheap plugpack will do the job.

Years ago I built a 3m tank which was firbreglass over plywood in a steel frame. The tank was 3100mm x 1200mm x 1000mm with a 950mm front window. The ply was standard building grade, 2 x 19mm laminated for the required strength. This was then covered with 3 layers of chopstrand mat and polyester resin to provide the final strength and to seal the wood. The inside was painted with matt black gel-coat. Where the gel-coat met the silicone for the front glass a special primer was used to allow the silicone to bond properly. The primer and silicone came from Ramset. The tank is still in use today at the National Aquarium. Points to consider when sealing a wooden tank. - The corner joins are under extreme forces. Any movement will cause cracking if the wrong sealing technique is used. Paint is no good. - A chamfer or cove will reduce the risk of cracking - Rubberised paint may work if it's thick and flexible enough. You may be able to get a primer to paint onto the acrylic to allow silicone to stick.

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Depends what the 'something' is. It must use a low voltage motor and have a standard universal switchmode power supply. It's a good idea as it makes 1 product usable internationally without the need for voltage adapters. It's happening more and more with electrical products - one power supply with a small clip-on mains connection terminal and a selection of terminals in the pack to suit all countries.

Been there and yes, it is rather an obscene waste of money. Impressive yes, necessary no. I'm sure they could halve the price of their cars if it didn't exist... I suppose they have to keep up their snob-value though. 8) Yes, I do have a BMW but I hate the whole snob-thing that seems to go with them! I only have it because it's a great car to drive, gets really good gas miles for the performance and I got it at a good price. Great fishy pics - I like visiting Aquariums in other countires too.

I've made a wood facade over steel before. Then you get the strength and good looks.

But you're not 15!!!!!!!!!!!!!!!!!!!!!!!!