48"x48"x14" tidepool plywood tank ?'s.

[sonofgaladriel]

Hello all.
I'm building a 'look down', shallow, tide pool, plywood tank to house some anemones, some LPS, a few hardy SPS, and a few clams. Small reef fish, mostly clowns, small wrasses, damsels. Scattered, shallow, limited rock scape. I like negative space with lots of sand exposed and all sides of the tank open.
48"x48"x14" tall with a water level at 13". 3/4" cabinet grade plywood.

Most likely will be using Pond Shield epoxy as I want a nice clean light blue or black, background with as few steps involved as possible.

I will install a front viewing pane of glass but most viewing will be top down.

Questions about the waterproofing.

If the seams are all well secured with glue and ample screws, is fiberglass cloth reinforcement needed in the corners for strength at these dimensions?
Will I be fine just siliconing the corners prior to the final coat of epoxy?
Open to suggestions and advice.

Aesthetic question

For this shallow, yet wide tank, light blue or black background? Light blue would help the tank look bigger and brighter, but black would make things pop.

Structural question

At 14", with 13" water level, is top Euro bracing necessary? Would 3/4" ply bow at this water level? I'd like to keep the top as clean and open as possible.

Will a pocket hole screwed and glued frame, made from 1x3 A grade pine, well glued and screwed to the front, be strong enough to support the glass and water pressure without a top brace? Kinda like a rimless look?
Thanks in advance for any and all help and advice.

 

[pisanoal]

I'm no expert in any of these areas, but I am in the process of building a plywood sump and used Pond Shield to seal it (great stuff, easy to work with). I opted out of the fiberglass corners, but let me explain why before you do the same. My sump is 6 feet long, and water level will be 12" in the first compartment, and 11-10" in subsequent compartments. I built several baffles into it and the longest horizontal run without a baffle is the 30"+ fuge section. I added a small brace up top in this section. The biggest concern with pond shield is that it does not flex enough with the plywood overtime and this can cause cracking, primarily in the corners. I think at my dimensions with the bracing I have from baffles and the one top brace, this should not be an issue. I will be adding heavy beads of silicone to all joints in case cracks do form in them. Also, one of the concerns with the fiberglass is trapping air bubbles. I've never done any fiberglassing before so that was a concern for me, although it doesn't look too difficult. Lastly, this is a sump in my garage and a failure will not cause any damage to my house.

As to the construction of your pool, I would recommend some type of bracing along the outside walls to add to the rigidity (some 1x2"s or 1x3"s horizontally like "ribs" screwed from the inside). This would look better then the eurobracing up top for a look down, and you skin over it with thin plywood if you wanted. Have you watched the pond shield: building a plywood tank, video on youtube? Bracing similar to what they have would be what I would consider for running 48" horizontal even at only 13" depth. You might even consider going to 1" ply instead of or in addition to the bracing. If you don't do any additional bracing, I would highly recommend the fiberglass route. If you do some bracing, you could feel decent about skipping it and adding a good bead of silicone.

I can't comment much on the front panel as I don't have one in the sump, and haven't put much thought or research into it. But I would steer away from what you are thinking with the PH screws and 1x3. I would stick with the standard ply tank construction methods and use a sheet of ply screwed in to the other walls like your back sheet. You can router out the hole for the viewing panel.

For color, this is obviously going to come down to personal preference, but I think I would prefer the natural blue look over the black. Even better if you are going bare bottom would be a tan bottom, with blue sides. That would look awesome in my opinion.

How much epoxy are you planning on buying? Based on my experiences (using oak plywood), I would recommend at least 2 1.5qt kits. I ended up using 3 but I had plenty for a couple extra coats, and even wasted about 1/4 of it to setting up too fast on my on one coat. I also had a bit more surface area to cover with the baffles. The first, thin coat doesn't go very far, and I used a whole 1.5 qt kit for it with only about 1/8th left. After that, I put 2 more coats on with the 2nd kit with a bit to spare, which I used to pour in the bottom and add some extra epoxy to the bottom seams.

I just did all of this in the last week so its still pretty fresh in my mind, hopefully that's of some help to you.

 

[ericarenee]

The plywood will for sure bow at the top causing it to pull on the corners and seems.

I would build this in a while it all locks together building two 4x4 square frames with a grove for the plywood sides to sit down into , The bottom frame with the grove facing up cut wall panels and glue into the grove.. Where the viewing panel is going to be use another 2x frame with a grove for the glass to slide into.. Once the sides are into the grove you can then glue the floor into place butting up to the walls..

when you glue it all together and put the top frame on it will all be locked together.. then calk the glass well apply fiberglass to all corners and to glass then water seal from there..
you can prob use 5/4 lumber or or ripe down some number 1 grade 2x lumber so that there are no knots..

Hope this makes sense...

 

[pisanoal]

The plywood will for sure bow at the top causing it to pull on the corners and seems.

I would build this in a while it all locks together building two 4x4 square frames with a grove for the plywood sides to sit down into , The bottom frame with the grove facing up cut wall panels and glue into the grove.. Where the viewing panel is going to be use another 2x frame with a grove for the glass to slide into.. Once the sides are into the grove you can then glue the floor into place butting up to the walls..

when you glue it all together and put the top frame on it will all be locked together.. then calk the glass well apply fiberglass to all corners and to glass then water seal from there..
you can prob use 5/4 lumber or or ripe down some number 1 grade 2x lumber so that there are no knots..

Hope this makes sense...

This is not the standard way to build plywood aquariums. I'd stick with what works and what everyone has already pioneered. Horizontal bracing along the backshould add plenty of rigidity to prevent bowing. Especially at only 14 inches.


Edit: I reread your post and if you did a grooved 4x4 frame on top and bottom that could work nicely. The only issue would be making sure the 4x4 doesn't come in contact with the water unless it's sealed.

 

[ericarenee]

This is not the standard way to build plywood aquariums. I'd stick with what works and what everyone has already pioneered. Horizontal bracing along the backshould add plenty of rigidity to prevent bowing. Especially at only 14 inches.


Edit: I reread your post and if you did a grooved 4x4 frame on top and bottom that could work nicely. The only issue would be making sure the 4x4 doesn't come in contact with the water unless it's sealed.

It would all need to be meshed in on all angles corners and around the window then finished with the waterproofing up and over the top , .. Without a top frame the top middle would Def Deflect out..

I know a thing or two about building and Structural support. Here is a tiny project i done not so long ago..

 

[pisanoal]

The ribbing I suggested would add the support. There is more then one way to support a structure.

Regardless, like I said, I like your idea for a few points. I think it will look nice and will add lots of support. Might be more difficult than the ribbing depending on tools available.

Sent from my VS985 4G using Tapatalk

 

[ericarenee]

The ribbing I suggested would add the support. There is more then one way to support a structure.

Regardless, like I said, I like your idea for a few points. I think it will look nice and will add lots of support. Might be more difficult than the ribbing depending on tools available.

Sent from my VS985 4G using Tapatalk

Yea i agree ...


Sometimes i forget not everyone has Fully stocked Shop....

I was thinking you were suggesting leaving the top rim with just the 3/4 plywood. It would not fail instantly but over time will stress the corners and cause a failure for sure..

anyway bed time for me..

I have several estimates early tomorrow then get everyone started on a Huge Tear out .. kitchen and bath while customers are on vacation s

 

[Joe Lydon]

Why not buy two of those cheap Lowboy tanks from ZooMed, use the side glass, and build a plywood bottom? Dimensions would be 48x48x10. Standard silicone bond for the glass, and choose any one of the tried and true methods of securing the bottom, with a retaining brace. You could actually build a 2nd tank, using the 24" panels that would be leftover. Save yourself a ton of headache. P.S. I'm not against building plywood tanks. I'm building one myself, but with the relatively cheap glass used on those Lowboy's, it's a no brainer.

 

[falcona2552]

Hey question everyone, so you screw and wood glue the panels together, and then fiberglass cloth and epoxy the seams?

What oz fiberglass cloth do you use? Is any slow cure 2 part epoxy good for this stage?

After the seams are all reinforced with cloth and epoxy, then do you pond armor on top of it?

 

[der_wille_zur_macht]

Hi falcona,

The tank is made like any other wood box, typically assembled with screws and glue. If you're putting glass in, you would apply that next, with epoxy. The epoxy used is typically a slow cure laminating epoxy. West Systems is a popular brand name but there are lots of others (I prefer US Composites house brand).

Glass weight and weave is somewhat subjective and depends on the specific application (tank size, etc). You're not shooting for a lightweight build here as if you were working on a boat or airplane or something weight-sensitive, so going thicker is generally not a problem. Still, there's a huge range in variation from one build to the next, and lots of people (myself included) don't typically use glass unless there's a specific reason to.

Regardless of using glass or not, you would next typically apply a waterproofing seal to the entire inside of the tank. One method that became popular years ago on wood tanks is referred to as the pour method. You prop the tank up so a given panel is flat on the ground, then pour several thick coats of epoxy on that panel. It will naturally settle out flat and with good coverage. Once that panel is done, you turn the tank so another panel is on the floor, and do that one. It saves the effort of getting a thick coat on a vertical or angled surface, which can be hard. The pour method is typically done with a slow cure laminating epoxy.

Besides the pour method, some people use other methods - gel coats, thickened epoxy that's brushed or rolled on, waterproof epoxy paint, and so on. If you dig out some old build threads you should get an idea. I put a bunch of photos in my 360g build thread which is years old, but the concept still applies.

 

[falcona2552]

Hi falcona,

The tank is made like any other wood box, typically assembled with screws and glue. If you're putting glass in, you would apply that next, with epoxy. The epoxy used is typically a slow cure laminating epoxy. West Systems is a popular brand name but there are lots of others (I prefer US Composites house brand).

Glass weight and weave is somewhat subjective and depends on the specific application (tank size, etc). You're not shooting for a lightweight build here as if you were working on a boat or airplane or something weight-sensitive, so going thicker is generally not a problem. Still, there's a huge range in variation from one build to the next, and lots of people (myself included) don't typically use glass unless there's a specific reason to.

Regardless of using glass or not, you would next typically apply a waterproofing seal to the entire inside of the tank. One method that became popular years ago on wood tanks is referred to as the pour method. You prop the tank up so a given panel is flat on the ground, then pour several thick coats of epoxy on that panel. It will naturally settle out flat and with good coverage. Once that panel is done, you turn the tank so another panel is on the floor, and do that one. It saves the effort of getting a thick coat on a vertical or angled surface, which can be hard. The pour method is typically done with a slow cure laminating epoxy.

Besides the pour method, some people use other methods - gel coats, thickened epoxy that's brushed or rolled on, waterproof epoxy paint, and so on. If you dig out some old build threads you should get an idea. I put a bunch of photos in my 360g build thread which is years old, but the concept still applies.

der_wille_zur_macht Thank you very much for your detailed and thoughtful response, you answered some crucial questions for me! I will be checking out your 360g build to familiarize myself some more as I am still in the planning stages. My experience glassing is with r/c airplanes primarily, and you are correct weight savings is everything in that application.

My take away is build the box strong, and make sure it is sealed properly.

 

[der_wille_zur_macht]

I did the whole R/C airplane thing too, many years ago. It's definitely a different ballgame. No one cares if there's a pinhole in an airplane wing, but a pinhole in a tank can ruin your life. No matter what technique you use, the important thing is just making sure you understand what you're doing and you know how to ensure there are no issues.

 

[falcona2552]

I did the whole R/C airplane thing too, many years ago. It's definitely a different ballgame. No one cares if there's a pinhole in an airplane wing, but a pinhole in a tank can ruin your life. No matter what technique you use, the important thing is just making sure you understand what you're doing and you know how to ensure there are no issues.

I read through your tank build, incredible work. I also checked out some other plywood builds, and I was wondering your thoughts on this sealing method.

After the box is constructed I was going to reinforce all of the seams with fiberglass cloth and 2 part epoxy resin. Would it be possible then to pond armor the tank and would the pond armor adhere to the resined seams?

Or if I am going to resin and glass the seams, should I just continue on and glass the entire tank. Because of the weird dimensions pour method is not going to work, and painting it on seems like it would take many many coats.

That is why I wanted to use the thick pond armor to seal, and glass for the strength in the weak points.

 

[der_wille_zur_macht]

If you're not going to do the pour method, I'd use a thicker laminating resin, tape the seams, then cover the entire inside with glass mat. It builds thickness quicker than woven fabric and IMHO is easier to work with since it's stiffer when dry. Make sure you get really good coverage with the resin on the mat so there are no pinholes. You could topcoat this with another coat of epoxy, or use the pond liner product you mentioned (which I have no personal experience with). You'd probably be OK without the mat, but again, I prefer overkill. Pouring marine epoxy is an easy way to get overkill, but since you've ruled that out I'd think about getting glass of some sort across the whole interior. It's a small tank so it won't be that expensive or difficult.

I would recommend building several small practice pieces with whatever method you want, until you have the whole process down and you know you can produce a result you like. None of these methods are super hard, but the risk is high for simple mistakes to cause major problems (again, pinholes!)

 

[falcona2552]

If you're not going to do the pour method, I'd use a thicker laminating resin, tape the seams, then cover the entire inside with glass mat. It builds thickness quicker than woven fabric and IMHO is easier to work with since it's stiffer when dry. Make sure you get really good coverage with the resin on the mat so there are no pinholes. You could topcoat this with another coat of epoxy, or use the pond liner product you mentioned (which I have no personal experience with). You'd probably be OK without the mat, but again, I prefer overkill. Pouring marine epoxy is an easy way to get overkill, but since you've ruled that out I'd think about getting glass of some sort across the whole interior. It's a small tank so it won't be that expensive or difficult.

I would recommend building several small practice pieces with whatever method you want, until you have the whole process down and you know you can produce a result you like. None of these methods are super hard, but the risk is high for simple mistakes to cause major problems (again, pinholes!)

Sorry for all the questions, but is there a special type of tape you need to use to tape the seems? Once I do that I will take your suggestion of fiberglass mat or cloth the entire inside of the tank. If I have extra I will probably glass the outer seems for strength as well. I like the overkill approach.

Is the US Composites epoxy resin you used suitable for my approach or should I look for a different type of resin? (Is the resin you used thick enough for what Im trying to accomplish in other words)

Many thanks to you for your time and feedback.