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Big Tank, you advice please


Pies

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Heya Everyone.

Well I am about to embark on my Marine Reef tank and the first thing I need is a tank!

So I am looking to get the glass cut tommorow, but now I am scared its to big and will not hold its weight in water.

ALL 10mm glass - 1600mm LONG, 750mm HIGH & 700mm DEEP (back to front).

Will this be OK? Will I need to brace the sides/front etc? I don't want to brace the front cause I will be using a shallow sand bed and it looks bad...

Bear in mind its for a reef so it will be 1/4ish rock, which will incrase the weight but reduce the pressure...

You 2 cents please...

Also no cracks about it being a baby tank since Warrens monsta effort! :>

Cheers

Pies

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Putting Rocks in the tank will not reduce the water pressure. The pressure on the side glass will still be exactly the same, but the force or effective pressure will increase on the bottom glass. If a very thick base is used, the glass will not need to be thicker than the sides. The base will need to be very flat and level however.

Based of the glass thickness calculator http://www.fnzas.org.nz/glassthickness.0.html

you need 17.09mm thick glass to get a good safety factor. If you use 10mm glass, there will only be 30% spare safety margin. Even the smallest assembly error will cause it to break. It will need bracing along the bottom edge and full length top bracing.

I would seriously advise against 10mm glass for a 750mm tall tank. My tank was 950mm in the viewing window and I used 19mm glass. The calculator said I should use 25mm but I could not find any. At 19mm it still had 225% safety margin. If you use 10mm you will only have 130% margin, way too small. Even 12mm glass will be pushing it as there will be only 187% margin. 15mm glass however would most probably be ok as there is 292% margin.

If you lower the height to 600mm you will be ok. So the long and short of it, no 10mm glass is not ok for 750mm. 15mm is probably ok.

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Hey thanks for the decipher of the calculator. I saw it on this site but really couldn't figure it out. I will reduce the height to 600mm and leave the specs the same. I'll also talk to the 'glass guy' tommorow and see if there is some thicker glass about for the bottom.

I'll also get full braces cut. I guess i'll just have to work harder to hide them :)

Thanks again.

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Hi Pies

I little trick, if you decide build your own tank. Tank builders who guarantee their merchandize know what the are talking about. They will usually not deal with you directly. So go to a LFS and ask for a quote with specs. Then the LFS will come back with the price and specs. No calculation whatsoever. Don't forget to ask for complete specs. like thickness, how many braces etc. Say you have to know because of the filter which hangs on the tank etc. etc. They do it for you, free. Then you know how to build it yourself.

John

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The problem with the LFS is they usually just guess. Sure you are covered by their warranty (kind of) but is it worth the hastle. They may provide specs etc, but do they have the engineering calculations for the tank to back them up? Haven't come across a fish shop yet that can, and yes I have visited most of the fish shops in Melbourne, Sydney, Perth, Brisbane and also most in NZ. Not one of them calculates the glass thickness required. They just learn by trial and error until they have tank sizes and glass thicknesses that don't break too often. How many of use have had a tank that has broken at some time, - most of use right. Well, not me. I've never had a broken tank in twelve years. I guess prior to about 5 years ago when I started to calculate all the spec for all my new tanks I got lucky. Since then I've upgraded the glass and bracing in many of my tanks. Not one has ever broken or leaked. I've also check unevenly loading the tank by twisted the base when the tank was full, still didn't break. I'm a little paranoid about earthquakes.

Not many LFS have tanks over 600mm tall because the glass gets too expensive. Most of the larger tanks that are readily available are made using 10mm glass. This sets the height limit to 600-650mm depending on tank length. They will custom make taller tanks but you need to start choping off arms and legs to pay for it.

Also, in NZ very few LFS make their own tanks and therefore know nothing about designing them. They are either made by a glass company or are imported. The glass companies are obviously cheaper to buy from.

There is also a lot of work in properly designing a tank to someones specification. With this in mind, is it really moral to ask the fish shop to spec the tank for you when you have absolutely no intention of buying it from them?

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Hi Warren

I think you misunderstood. I live 2 minutes from a professional tankbuilder. But I cannot buy from him. I have to go to my LFS and HE orders from HIM, the builder. Who knows what he is doing. I never said the LFS builds it. I am convinced that the professional tankbuilder, who has 5 men working for him and gives 2 years warranty on his tanks and sells to all the vitorian LFS's, knows his job.

John

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Well its here! Thanks for the advice Warren I have used it and reduced the height of the tank to 600ml. I have also had extra braces for the top and bottom cut.

So assembly is about to begin. I need a hole drilled in the bottom for plumbing my Dorso Standpipe, and the people who cut me the glass could not drill a hole larger than 25mm and I need a 32mm hole drilled. So i'm off to take the 'bottom payne/pain/pane' elsewhere tommorow.

All up the glass cost me $400.00 for the 1600x600x700 tank with bracing. Keep in mind that its all 10mm glass but this tank has no lid like a traditional tank, just bracing (i want lots of evaporation).

So now its onto Silicone. Anyone have any thoughts or know brands to use (or avoid). I'm eager to start.

Ohhhh and a last question, for my overflow box am going to use perspecs (sp?) for the divider. Is there any special considerations for attaching perspecs to glass? Will the normal silicone work?

Cheers

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In response to John,- maybe he does, maybe he doesn't... Go ask him to show you his calculations then I'll be happy.

Well done Pies, lots of luck for the assembly process. I've had really good success with only one brand of silicone. Every other brand Iv'e tried let go on my test tanks so now I stick with just the one.

Use FOSROC Silaflex RTV glass sealant. It comes in a white tube with blue writing on it.

As far as glass preparation goes; use methanol to clean the glass (if you can get it). Alternatively, use Meths that has no die or flavour added to it (so it should be clear). You only need to clean the areas that the silicone will contact. Rub the area with a lint free clean rag with the meths on it. Immediately wipe the residue away with another clean rag. Once you have finished, throw the rags away and get 2 more. Repeat the process.

Do this as late as possible, - just before you silicone if possible. Leave a few minutes to allow any missed meths to evaporate.

Do not touch the cleaned areas with you hands. It possible wear cloth gloves while moving the glass around to reduce the risk of get skin oils on the glass edges. Mask the area just inside where the silicone goes. It makes the cleanup job easier.

Apply just enough silicone so that the air bubbles squish out as the surfaces mate. A little experience and you get it sorted. If you work the glass side to side just a little as the surfaces mate, it makes the air bubbles come out easier. Do not push the glass surfaces completely together. When glass is cut it has an uneven edge. If a high point contacts the other glass surface it can cause a future crack. If you've had the glass ground flat, square and polished then tank assembly will be really easy and the joins will look awsome.

Good luck, let us know how you get on.

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OK well its official. I have brought the Silicone this morning. I got the hole I needed drilled into the bottom payne. I have got the last of my pressure piping plumbing. Everything is ready... All I need to do now is build up some courage... Ohhhh and get a frame made (to hold the tank and house the sump), tossing up between wood and metal. I can build a wooden one myself (will sit on a concrete floor), but if I go metal I need someone else to build it. So it will prolly be wood. Will think longer on it today.

Thanks for all the help and advice. I will start the tank in the next few days. Should it be built in stages or all at once? All at once prolly.

Cheers!

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:) The English language can be quite fascinating at times with the way you can juggle words :)

I'd say I use the same stuff as you. It seems you've been around a little longer than me. Its good stuff wot!

Should be "Both Warren an I use the same brand of silicone" :):)

In the early days it was Dow Corning that had the monopoly in the silicone market, but now there are several brands, and finding a proven one can be expensive, in more ways than one, but the one mentioned in Warrens post is completely reliable.

Hi Pies,

"payne" ... Could be a persons name.

"pane" as in glass :) (Just a bit of fun... not meant as a correction :)

Personally, I would seal it all in one hit for better continuity of the seams.

Laying new silicone on the top of previously cured silicone is always a risk IMO.

It should be well cured by the time you get the stand and cabinet built, but I would leave it at least a week for a tank of that size.

Regards,

Bill (Pegasus)

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OK I brought the Silicone you both recomended (5 tubes should be enough?).

I have all the glass sitting behind me and I am shit scared to continue. Tommorow could be the day.

Thanks for all you help guys, I have listened and feel a lot better for it.

If anyone has and web site links or info on building a secure cabinet for a tank, please share them with me :) I am not a joiner, so its going to have to be simple, yet robust. I am going with all wood as I am worried about the salt water and RUST...

On another note, Warren, I have installed 3 (of 6) 4ft fluro tubes of the type you recomended elsewhere on this site. I brougt Sylivana tubes, but they gave me a philips -> sylivana reference card the converted them to be. I brought 2x 6500k 1x6000k. The colour is VERY pleasing to the eye, which I was concered about. But the best thing is the my plants have responded to it. I mean, I am sure I saw a difference in my plant leafs/shape/colour in less than a day! So i'll keep an eye on it, but so far I think I have found my new standard freshwater tube selection. Cheers!

Cheers

Pies

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Tank stand plans:

http://www.garf.org/stand.html#STAND

I glued as well as screwed mine for strength (Gorilla Glue). To hide the base of the tank, sand, and polystyrene sheet bring the sides up a couple of inches higher then the top of the frame.

You might want to use waterproofed ply (treated or epoxy sealed) for the top as I think water could be trapped under the polystyrene sheet beneath the tank from spills etc and slowly rot.

Plan your sump system out before making it so you know where to add shelves etc during the construction. If you put a back board on then you will have to cut out holes for the plumbing and wires before putting in place. Adding more afterwards is difficult if its against a wall (who me? :oops: ) Take your time planning and making the stand since once the tank is on you can't change anything.

Have fun

Cheers

Shilo

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