Building a Stand

[Luca Brazzi]

I started building the stand for my soon to be 75 gallon drilled acrylic tank. Im using a basic 2x4 frame design. The top and bottom look like this:

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The top and bottom are connected by several 2x4 uprights. The thing I learned about this is that you have to construct things just right so that the weight of the tank is resting mainly on the upright beams and not the screws/glue etc.

I do have one problem though... In order to be able to get my sump in the stand once its built, I have to leave out one of the beams, however I think that I can solve this problems by drilling a couple of holes in the top and bottom and though the beam, and attatching this beam using a countersunk bolt and nut on the once the sump is in place.

So far the stand seems rock solid. I used lots of glue and 2 1/2" screws. Im planning to cover the stand on 3 sides with 1/2" plywood with doors in the front.

[Darkangel]

You do not need all that support for a 75 gallon tank. That is more then my 90 has. When you build the stand notch out the uprights so that the cross member rests on the upright. In this way you can lag bolt it together and never ever worry about it again. The wood will rot before the joint comes apart. If the picture works you will see what I mean. If not go here: http://photos.yahoo.com/bc/tippmann_dad/lst?.dir=/My+Fish&.view=t it is the last picture. If you are still worried you can double up the corner with two 2x4's. At the most one set in the middle but you do not even need that. I am of course going on the guess that the tank is 4 feet long. If it is 6 I would put in a middle brace cut the same way as well.

[agilis]

I made the stands for my two big aquaria with a very similar design, if I am reading your diagram correctly. I used two sheets of marine grade plywood, one as as the floor and one as the ceiling of the stand, with upright 4x4s and 2x6s as the columns sandwitched between the plywood sheets. It was critical that the upright columns be exactly the same length, and have exactly squared tops and bottoms. After all the wood was cut, the stand had to hold together flush and straight before any screws or gluing.. I used a 4x4 post in each corner, and two 2x6s set longways on the front and back edges. The two in front are set farther apart, leaving enough room to manuver the wet/dry filter into place. A third upright support for the front is set in place dead center, to compensate for the wider gap between the front 2x6s.This support is a 2x4 that sits in place without any screws or glue. It is firmly held in place only by the tank's weight, but can be removed when the tank is empty. There are also a couple of short 2x4 braces at each end, between the corner columns. The top side, where the tank sits, is covered with a sheet of the tough rubbery stuff they use as hallway floormat runners. This provides a thin but effective buffer between the wood and screwheads, and the tank's plexi bottom.

The stands are as solid as a rock, but are incredibly heavy when fully assembled. One is 72"x24", the other 60'x18".

[carpguy]

That seems quite heavily built. How big is the sump? Could you slide the two inside braces out to fit? I don't really think you need to stay 16 on center on a cabinet. Could you work in a header:

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[Luca Brazzi]

I built a modified stand based on the diagram shown at www.garf.org where there are 2 uprights for every crossmember.



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However, since the stand is 21" deep OD, if I was to orient the uprights the way they show, The inside dimensions would be 21" - ((1.5" x 2) (thickness of a 2 x 4) + (3.5" x 2 width of a 2 x 4)). This would leave me with 10" front to back inside the stand.

My sump is 14 x 30", so what I did was orient one beam sideways to allow room front to back for the sump:



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The other problem is that I need to be able to get the sump in and out of the stand. That being the case, I need to leave out one upright as in:



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Missing Upright



This way, I have a space large enough to move the sump in and out. I like the idea of placing a "friction fit" upright in the place where the missing one is though agilis.

Oops... I didnt notch... I should have waited till I got a response before I built (****). You're right Darkangel... notching is the way to go. I should be ok though anyway right?

[agilis]

The sump under the 180 is a standard 29 gal. tank, 30 inches long. It can be manuvered into the stand from the front, with the removable center support out, but only because there is about 10 inches of space behind the stand. Alternatively, the whole stand can be dragged out from its alcove, and the sump tank can be slid in from one of the sides. There is 30 inches of interior space between the top and bottom, the length of the upright supports. The sump under the 120 high is a 24" 20 gal. Both wet/dry filters are DIY, and basically identical.

You are absolutely right, the stands are way overbuilt, far heavier than necessary. The sumps, external Iwaki pumps, and external protein skimmers totally fill up all the under tank area. There is too much wood and not enough room to work in.

These stands and the tanks on them were my first large aquarium project, and I would do things differently now. Easy access, space, convenience for maintenance, for moving or removing items, etc., would be a big priority.

On the other hand, the plumbing system compares favorably with most of what I've seen, and I would do very little differently in that area if I were building another system today.

[Luca Brazzi]

Oh yeah... you mentioned plumbing... Ive got a question about that too.

Since Im drilling the bottom, I purchased 2 bulkhead fittings. A 1" for the drain, and a 1/2" for the return. Both are threaded on the tank side and slip fit on the bottom. I also have a 1" bulkhead on top of the biotower in the sump I built. Whats the best way to do the plumbing? Will PVC cement work on a bulkhead fitting? Should I permanently cement a piece of PVC to the fitting, and then use PVC for all the plumbing, or should I use some kind of hose?

[agilis]

Hi, and season's greetings.

I assume when you ask about pvc cement on the bulkhead fitting, you mean the slipfit opening outside the tank. The inside tank section should seal with an o ring.

To start, let me advise you to cement the overflow tube that projects upward to the water surface from the tank bottom bulkhead fitting. Anything else, including the use of silicon to hold a section of pvc standpipe in place , can end in disaster. The drain/overflow fitting and pipe should be totally sealed as close to the surface as possible. You can also use threaded sleeves for pipe connections. You can have a removeable section near the top for fine adjustments of water depth. This, btw, is another reason I don't like bottom of the tank holes.

Beware of bulkhead returns below the water line. Reverse siphon is a certainty, and I don't trust those one-way water valves. I've seen them fail. Better to have the return line come in over the take side, with a return stem slightly submerged. It's safer, and you can direct water flow as you choose.

Yes, you can use pvc cement to attach pvc pipes and fittings to the bulkhead, which is almost certainly made of heavy grade pvc. It seems to me that if the outside section of the bulkhead is a female slip fitting, you would have to cement in a short section of pvc pipe, even if you use vinyl hose to carry water to the filter/sump. You might as well cement in a longer length, being careful not to make future disassembly difficult.

I use permanently cemented pvc pipe from the overflow bulkhead fittings up to the last 12 inches before the top of the wet dry filter. This is so that I can open and move the cover to the filter, which is a section of 3/8"glass drilled to accept three bulkhead fittings, one for each of the side-mounted overflow fittings. This also allows me to easily visually inspect the short section hose and hose clamps. This glass is the fitted cover to a 10"x20"x15" plexi box the bottom half of which sits inside the 29 gal. sump.

Two inches under the glass cover is a drip plate. The plexi box holds about 8 gallons of bio-ball type media, and there is about 10 inches of water depth in the sump, under the plexi box.

Permanently cemented pvc pipe will not loosen or dry out, like vinyl hose. It's very safe stuff. Plexiglass tops to anything will inevitably warp, which is why I use a glass cover. Much more expensive, but worth it. I hope all of these verbal descriptions are reasonably clear. I recently bought a good digital camera, but have not yet progressed to the level of being able to post or email pictures. The instruction booklet is the size of a novel.

[superstein61]

Originally posted by agilis
You can also use threaded sleeves for pipe connections.

True but I would add that if you do, be sure to use some type of pipe compound on the threads. Especially if it is on the return line to your tank (and thus pressurized from the pump). If you don't, you will likely get some water creep at some point in time

Speaking from experience, using staight slip connection PVC pipe glued with PVC cement is far better than any threaded connection IMO.

[agilis]

Superstein's point is well taken. I do not not use threaded sleeves outside the tank, except as the last connection to the Iwaki that drives the system. Just ahead of that sleeve fitting is a gate valve. A good wrapping of silicon tape on the threads prevents any leaks.

When I suggested threaded sleeves, I had the inside tank stand pipe in mind, not external fittings, and then only as something preferable to the slip fit with silastic that I have, to my horror, seen some people use. Have the power go off for a few hours and the entire tank contents may drain. Any failure of the structure associated with a hole in the bottom bulkhead will be a catastrophe. Bulkhead drains mounted on the tank back wall, just below the water line, will not compromise the watertight integrity of the aquarium below the bulkhead, no matter what happens.

[Luca Brazzi]

I hear you agilis... however, having a bottom drilled tank does not necessarily mean that you can drain the tank through the hole in the bottom. In my setup the holes in the bottom of the tank are inside a watertight overflow box with holes in it near the top of the tank. If my bulkhead fails, I will only lose about 4 gallons of water because when the water level drops below the holes in the overflow, it will stop flowing to the drain. I guess if I were to also have a leak in the overflow box then I could lose more water but the overflow is cemeted to the tank using acrylic cement, and a bead of silicone so it is unlikely.

I did a system test today (tank, stand, sump) and I had to PUMP the water out of the tank using a python.

I do have another stand question though...

During my system test, I sprang a leak!

It was about halfway up the side of the tank (I guess I must have missed a spot when I was cementing the tank together). Anyhoo, I ended up leaking a gallon or 2 onto the carpet (luckily I have a steam vac). So after I drained down below the leak, and cemented and siliconed it, I then refilled. I noticed however, that some of the water spilled onto the stand, as well as the floor.

When I finished the system test, and drained the tank, I took a look at the stand and noticed that there were a few places where the water had contacted the glue, and the glue was becoming unglued.

So the question is... What can I treat the stand with to make it waterproof? Can I use the same stuff I used to seal my deck on plain old 2x4s? I'd like to waterproof the stand before I cover it with plywood, then seal it again.

[agilis]

Leaks in plexiglass tank seams are not good, and can be a symptom of structural problems. When filled, the strain of water pressure will cause the plexi sheets, especially the longer sections, to bow outward. The thinner the plexi, the greater the bow. If those seams are not solid, and/or if the plexi is to thin, the flexing itself can tresult in leaks, or even tank failure.

I've never constructed a large plexi tank, but I know the fabricator who made mine, and watched him at work. I know that the edges have to be exactly straight, with both pieces making full contact the whole length. The bonding chemical was applied quickly, with a special applicator, while the sides were held tightly in place with wooden vices. The bonding chemical would instantly penetrate the seam totally, in effect chemically welding that seam. There was no use of silicon, which in any event does not bond completely to plexiglass, cannot be relied on even as a caulk. Silicon/silastic should not, inhp, be used on anything except glass. I know it can be used for other things, like building rock walls, but it cannot be used for structural or waterproofing purposes except on glass.
You should not use silicon as a seam caulk on a plexi tank. It will only temporarily mask structural defects. A plexi tank MUST be absolutely watertight and solid using only the bonding chemical.

I think that a DIY stand should be held together primarily by strong stainless steel screws. Glue is secondary, and not to be trusted in any high stress application. Glues should be high-tech high strength, not carpenters glue, whatever the package claims. Glue should also be totally waterproof. A good quality professional epoxy or urethane is all I would use.

I suggest using only first- rate materials. It is safer and ultimately cheaper. There is nothing worse than having to start all over with new materials because you cut corners the first time. I hope the plexi you are using is thick enough for the tank size. I would use nothing less than 3/8 inch on a 75 gal., and then only if it is less than 20 inches deep.

[Luca Brazzi]

The tank is made using 3/8" plexi, and is 18" deep. All of the seams have been cemented together using acrylic cement. I used thickened acrylic cement to weld together the one slight gap I had on one side of the tank (about 1" long), the Silicone sealant is only used as second precautionary seal NOT for structural purposes. I also have a 12" wide centerbrace welded across the top of the tank to prevent bowing ( I may put another cross brace at either side of the center one). After I cemented/siliconed that one leak, I refilled top the top and there was no bowing whatsoever.

As to the stand issue... Youre saying I should coat the entire stand frame with poly urathane?

[agilis]

Urethane is a high tech adhesive. It has nothing to do with polyurethane. Urethane adhesive can be hard to find. I get mine from sporting goods stores where it's sold as a repair substance for waders. The fine print on the packaging will tell you it is urethane cement. It is great stuff.

If your stand is already assembled, I'm suggesting big screws or bolts be added as the main thing holding it together. I'm suggesting that the stand should be fully secured even if the glue were not there.

Instead of silicon added in a tank corner where there is a gap, it would be much, much, MUCH better if you use 3/8 or 1/2 inch square plexi rods cemented in each inside corner. This will give extra adhesion surface, make the tank a lot stronger, and cover any tiny gaps. Also line the inside bottom edges where the sides and bottom sections meet the same way. Believe me, you will be glad you did. These rods are perfectly straight, and should be available from plexi dealers. It is not a good idea to try cutting your own, because you will not be able to get the edges as perfectly straight as the prefinished rods. Forget about silicon. It will separate. Not "might". It will.

Don't rush the job. I know it can be hard to wait when you are close to being finished, but these final touches are critical.

[Luca Brazzi]

Thanks for the advice...

I think that the rods will be a great idea for even more seam strength.

For the most part, the seams in the tank are very good with little or no bubbling. That one area where I had the leak was due to the fact that I had missed cementing that 1" altogether (something must have drawn my attention away). I did have to cut some of the pieces myself because my acrylic dealer goofed the sizes but it was too late for me to argue the point (this is why I ended up with an 18" high tank instead of 20). After cutting the pieces, I used a scraping gizmo I got from the acrylic dealer to remove the saw marks.

As for the stand, The glue is NOT used for the main structural integrity. I used 2 1/2" deck screws to assemble the 2x4s (8 screws in each upright and crossmember) and the stand would be rock solid even without the glue. I coated the entire frame with a 3 year severe weather deck sealer. The way I figure it, if the stuff can last 3 years OUTSIDE it should last forever inside with an occasional drip here or there. Remember, Im going to be covering the entire frame with plywood (3/4" for the top) which will also be sealed so in the finished stand the frame should rarely if ever see any real moisture other than what evaporates from the sump or an occasional spill. Most of the plans Ive seen for 2x4 frames dont mention sealing the frame lumber at all.

[agilis]

Good Luck. It sounds like you are on the right track.

I hope you keep us updated about how everything words after the system is up and running.

[Luca Brazzi]

Now that I have the frame built. Its time to think about the covering. I went to the local Home Improvement store today looking at lumber. I think I want to gow with 1/2" birch plywood. I plan to permanently mount it to the back and the right of the stand using nails and glue. To attach the front and the left side Im thinking of using Industrial strength Velcro. This way I can completely remove the front and one side (the side where the drain and return plumbing is) very easily for accessing the plumbing.

What do you'all think?

[Luca Brazzi]

For the covering... what I did was to cut 4 panels. 2 for the front, and one on each side out of 3/4" Birch plywood. Since the frame is the actual support system I didnt need to use the pnales for structural purposes (just decoration) so I sealed each panel with a deck sealer, and velcro'd them to the frame. This way I can pull all of the panels off if needed to get underneath and work on the plumbing. The Velcro strips left gaps between the pieces but all of that will be covered when I put the corner moldings on. I will also be cutting a couple of rectangular openings in one or to of the panels for doors so that If I want to get something quick, I dont have to un-velcro the panel... just open the door.