10'x14' 2500 Gallon Plywood Stingray Pond

[JohnG]

A friend and I have been building a 10'x14', 2500 gallon, stingray pond for the last 6 weeks, almost done with it now. The pond is being made entirely of 2x4s covered in plywood. Rather than doing a 2x4 frame we actually built it out of solid 2x4s for extra strength, probably overkill I know. The wood is being coated with fiberglass, resin, and epoxy paint. We are installing 2 8'x30" acylic windows for viewing. Here is the parts list:

1 Unit of 8ft 2x4s (A unit is basically a pallet of 2x4s, about 275 of them)
10 Sheets of 1/2" Plywood
To many deck screws to count, best guess would be in the 4-5k area.
2 8'x30" 3/4" thick acrylic windows
12 Gallons of Polyester Fiberglass Resin
9 Gallons of Max ACR Epoxy Fiberglass Resin
3 Gallons of Sweetwater Epoxy Paint
About 100 Sqft of fiberglass matt
10 - 1" Adjustable eyeball output bulkheads
4 - 2" Screened intake bulkheads
24 Tubes of Dow Corning 795

Please forgive the quality of the pictures, they where done with a cellphone camera.

Part 1:

First we made a 10'x14' 2x4 frame to build the pond on. Its done in 4 sections, an 8'x8', 8'x2', 6'x8', and 6'x'2'. Did it this way since we where working with 8' 2x4s. Then we screwed each section together to make 1 solid frame. The space between each 2x4 is no more than 12". To connect 2x4 to 2x4 we used 2.5" deck building screws throughout this entire build. 2x4s are really only 1.5" thick so a 2.5" screw works great.

 

[JohnG]

Next we layed down 2x4s to make a floor for the pond. Each 2x4 was screwed into each of the 2x4s in the frame below them making a very strong floor. Then we started on the walls, in this phase doing only the first 2 layers of the walls. The walls are being done 1 2x4 stacked ontop of another. We used an interlocking corner design for extra strength.

 

[JohnG]

Next we had to make the space for our windows. We had one corner that was going to be just 2 short sections so we built that one up all the way to the top of the windows. We then started building the other walls up the the height of our intake bulkheads.

 

[JohnG]

We left holes in our 2x4 walls of 6"x6" for the intake bulkheads, then near the top we made 6"x4.5" holes for our output bulkheads. At this point we have the walls built up to the top of the windows.

 

[JohnG]

Next we finished building the walls, in this section you can see the wholes left for the windows with the top of the frame on them now.

 

[JohnG]

Next we layed 1/2" thick plywood down over the floor of the pond, and did the same for the walls. I don't have any pictures from right after adding it to the walls but you can see it done in Part 7.

 

[JohnG]

Next we used fiberglass matt in all the corners with polyester fiberglass resin. This was done in the 4 corners and where the walls meet the floor, the places that need to be the strongest and where we are most likely to have leaks. We considered coating the entire pond in this matt but decided we would rather shoot ourselves. The matt we where using was very loose and difficult to work with, and absorbed a tone of resin, if we had better fiberglass matt it probably wouldn't have been so bad.

Before begining with the fiberglass we also went through the tank with Bondo and filled in any holes or large cracks that resin would not fill in, giving us a nice smooth surface.

A note on polyester resin, we used to do the first few layers because its cheap ($40 a gallon) compared to epoxy resin ($90 a gallon and not available locally). Polyester resin should not be used as a final coat as it is not fish safe. As you will see later we are sealing it in with epoxy resin and paint.

 

[JohnG]

After the fiberglassing in the corners had dried we went ahead and layed down a coat of polyester resin over the entire pond, this was done using paint rollers. Other than the fact that the stuff smells horrible it was pretty easy to put on. We did 5 coats of polyester resin using about 12 gallons of resin, each one waiting about 24 hours for it to dry.

 

[JohnG]

Next we started with Max ACR epoxy resin, we used 7.5 gallons of epoxy and did 3 coats. This stuff doesnt smell much but you still need masks, its a little thicker than polyester resin and you have to mix the hell out of it or it wont dry, as we found out the hard way. It also requires 3 days of cure time. Max ACR is specifically designed for building aquariums and is safe for the fish. These pictures are after we had gone through and sanded the epoxy resin for painting, you can also see we have cut our bulkhead holes at this point.

 

[JohnG]

We did three coats of the Sweetwater epoxy paint, using 1 gallon per coat. We used extension rollers to do this, waiting 24 hours between each coat. This stuff smells worse then the polyester resin (we could smell it through our masks and we had the most expensive ones homedepot has) but went on very easy, just like regular paint. It requires a 7 day cure time. We did this coat on Thursday the 10th, so now we are waiting on this to cure and then will install our windows and bulkheads.

I am currently considering weather to leave this as a bare bottom pond or use pool filter sand. I saw alot of posts from people who have used pool filter sand with rays, but only 1 post complaining about it sticking to the rays disk, so I am wondering if this is a issue with all pool filter sand or if there are different types? Any insight would be appreciated.