A Successful Mix of Water and Wood

This article is from Issue 14 of Woodcraft Magazine.

Cutting the frame

The aquarium will have a substantial, durable frame that will require some muscle to cut and assemble. Handling 4' x 8' sheets of 1"-thick plywood requires an assistant or a good set of roller stands (Fig. 1). 

Cut both sheets of plywood to 65". Measure 23" from the long side of one piece, or set your fence to 23" and rip the back left side. Mark or reset your fence to 24" and rip the remainder of that sheet for the back right side. It’s important to save all the offcuts for later use.

To cut the front panel, lay the board with its best side down. Mark lines 9" and 18" from one side; from the other side, mark in 22". Rip the line you drew at 18". Now set the saw to 45° and, with the best side down, rip the 18" piece at the 9" line.  

Leaving the saw angled, cut the remaining 30" at 22", making sure the best side is down.  You may need to set up a fence to keep the angled board straight. Turn the 22" board around and rip the other side, keeping the best side down, so that both sides are cut at 45°. The best side should be the wider one. 

Assembling the tank

As your aquarium takes shape, take the time to make sure all joints and dadoes are lined up as closely as possible to save sanding time later. Be careful when gluing and wipe glue off as soon as possible to save sanding places where sanding will remove too much material or may interfere with the bonding of the waterproofing and woods.

Assembling on sawhorses or a table will be less stressful physically than assembling from the floor. Gather the following to have at hand before beginning: drill with screw bit and countersink bit; screws; claw hammer; rubber mallet; medium clamps (4"-12"); glue (in a bottle with a tip is best); and a bucket of water with an old rag.

On the outside of each piece, eyeball the middle line of the dado and mark it; this will guide you in placing the screws. Lay the two back pieces on the platform, dado side facing up, with the 23" piece (A) on the bottom. Lay a glue line along one whole inside edge of the 24" piece (B). Pull that piece (unglued side) toward you, and stand it up when it reaches the edge of the other piece so the glue line is facing the edge of the bottom piece. Fasten the two together, being very careful to ensure that the two back pieces line up exactly. Countersink holes every 1½" to make the installation of the screws easier and to prevent breakage. 

Next, place a glue line in the dado groove for the tank floor (piece F)  and put this piece in, tapping it if necessary with the rubber mallet (Fig. 7). Place screws carefully; if you miss and can see the tip, remove the screw and try again. Countersink every 1½" and place the screws.

After securing the floor, glue and place one side on, matching 90° angles and making sure the window is at the top. Be careful not to use screws so long that they might pierce window or door openings. 

Screw side (D) to the tank floor before screwing the side to the back. A clamp helps hold it straight (Fig. 8).

Place a bead of glue where the second side (E) will attach and place the second side, tapping it in to get a good fit. Again, attach the floor screws before rotating the unit and placing the side screws.

Lay down the front side (C) with the dado facing up. Lay a bead of glue along both sides from top to bottom. Put the front in place, line it up and secure it with one screw. Draw a screw line for accurate placement of the screws into the tank floor (Fig. 9). The alignment of countersink holes is critical here as well as the placement of the screws to hold the front (Fig. 10).

To prevent the front of the aquarium from sliding out of alignment as you place the screws, clamp the two pieces together (Fig. 11).

Supporting the tank floor

You’ll need to find all those offcuts from earlier and grab a tape measure. Turn the aquarium upside-down, or if you can manage, leave it on the table. From the scraps, cut pieces G and piece H to support the tank floor. Place a bead of glue along each joint between the floor of the tank and the underside, even with the dado. Glue the supports in place according to the illustration on page 23. There are no supports attached to the two narrow side pieces.

Cutting the back opening

The back opening(s) vent the filter and provide a hidden place for electrical cords. If you don’t plan on moving your aquarium, you can cut only the side the electrical outlet is on. We always cut both sides in case the client moves the aquarium.

One of the advantages of the lower cabinet is to hold excess water, should your power go off and the water overflow the filter. This is rare, and if you have your filter/water level calibrated efficiently there should be no spillage; but it does occur and you should cut the opening high enough to preserve this holding capacity.

With this in mind, measure 4" up from the bottom on the inside of the aquarium; this should be close to 7" on the outside. Drill a pilot hole here. On the outside, draw a line parallel with the bottom at the height of the hole. The remaining dimensions are not written in stone; about 6" in from each end and 12" above the bottom line should do. You can use a jigsaw to cut the opening, as it will be hidden when you install the aquarium.

Cutting the overflow

On the inside of the upper tank portion, you will need to measure from the bottom of the tank to 1" above the window opening. (This should be approximately 32".) Cut a piece from the remaining scrap to that length. With your table saw blade at 45° and the fence at 11", run the piece you just cut through so the side is angled. Rotate it 180° and cut the other side at 45° as well. This panel (piece Q) will fit up against the back corner of the tank to form the overflow.

Waterproofing

System Three General Purpose Epoxy Resin is a two-part epoxy coating that infuses into the wood rather than sitting on top of it. It was originally developed for the boat-building industry, but woodworkers are continually finding new uses for System Three’s environmentally friendly products. 

Mixed at a two-to-one ratio, this product will cure at temperatures as low as 35° F. When fully cured, it is unaffected by water, oil, kerosene, and many other chemicals. It will not stain wood and is immune to fungus and rot. It is unique in that it may be applied to damp wood, provided the adhesive is worked well into the surface.

System Three is odorless and colorless. Pigment may be added as desired; we recommend the top portion of the aquarium be tinted black. Black is desired because it gives the viewer the illusion of depth and is unlikely to show algae.

If you are adventurous, you can buy one gallon and divide it in half; tint one half white and the other half black. It does come in half-gallon sizes, which might make tinting easier. Follow System Three’s instructions for tinting.

Take care to protect clothing, hands and surfaces when applying the epoxy. Purchase cheap brushes or rollers, because you will have to discard them when finished. The applicator of choice can be placed in a plastic bag and stored in a freezer for use on successive days. 

There is no need to sand or prepare the inside surface of the aquarium prior to applying the first coat. Paint the top portion of the aquarium and the overflow black, and the lower portion and lid white. The white lid will reflect the light and the bottom compartment should be white so the filter and electrical items are visible. 

Using a disposable brush or roller, apply a liberal coat of black to the inside of the upper portion of the frame you’ve constructed, making sure to get into the corners and joints, but not leaving excess epoxy there. Getting epoxy on window openings is desirable, but keep it off the outer portions of the frame. Paint one side of the overflow at this time. Somewhere on the outside of the frame mark this coat. You will be applying six to 10 coats of epoxy, so keeping track is important. 

You can apply more than one coat per day if you begin early and it is warmer than 72° outside. If the epoxy feels solid and dry, sand lightly and apply the next coat. You need a minimum of seven coats if you plan to ever move the aquarium. Make sure to paint both sides of the overflow. 

Lid construction

Drill a 2" vent hole in the back corner of the lid (I). Cut a piece of ¼" oak plywood (R) to the size of the lid, plus ½" on the three front edges. 

Apply contact cement to the lid and the back side of the oak ply lid covering (Fig. 13). When it has dried, carefully lay the pieces together and press with a roller. 

Make a pilot hole in the oak using the vent opening as a guide, and rout the oak to match the lid vent hole (Fig. 14). Cut the edge of the oak flush with the lid (Fig. 15). 

With a sanding block, carefully sand from the interior of the oak lid to the exterior at the edges, following the grain. This will smooth the edge grain back into place. 

Using a ¼" roundover bit, round the edges of the trim that will be affixed to the three front edges of the lid.

Cut the trim to size. Cut one end of the two short pieces (S) and both ends of the front piece (T) at 22½°  (Fig. 16). Affix the trim with 1¼" brads.

Mix some of the white waterproofing and coat the underside of the lid, making sure to get into the crack between the trim and the lid itself and in the vent hole, but not onto the outside of the lid or trim (Fig. 17). This is a good time to waterproof the bottom compartment of the cabinet as well.

Installing the glass

Move the aquarium to a location where it will remain undisturbed for 24 hours. Check that the edges of your glass have been deburred; if not, do so with a block sander. Also have all your equipment and the hose ready to fill the aquarium. You have approximately 30-45 minutes to insert all the glass pieces and fill the aquarium to achieve optimal results. You will need: block clamps; homemade wood block wedges, rounded at the ends, 1" x 2" x [the measurement of the opening to the back wall]; three tubes of Dow Corning 732 silicone caulk; silicone gun.

Using a coarse file, remove all the waterproofing “nibs,” those drips or drops which have formed on the opening for the glass. Apply a liberal coating of caulk all around one side opening (Fig. 18). Make sure to vary the pattern and spread the caulk out 1"-2" beyond the opening. You cannot use too much, but too little will cause problems creating a watertight seal. 

Lay a bead of silicone along the three front sides before placing the windows. Carefully place the bottom of the first panel of glass on the bottom of the tank. Make sure it is square with the window and press it against the silicone (Fig. 19). Wedge the glass in with your wood blocks (Fig. 20) until the silicone squeezes out the cracks between the glass and the wood 1/4". You might want to place a piece of cloth between the wood and glass. Press gently but firmly in place. Place a clamp over the top of the aquarium to squeeze the silicone flat (Fig. 21).

The silicone should be evenly distributed under the glass. Also squeeze a bead around the edge of the glass, then use your finger to smooth it out evenly. Repeat this process with the second side and then the front piece.

After all three pieces of glass are installed, fill the aquarium so the water level just reaches the top of the glass.

Hopefully you have placed enough caulk so that you won’t have leaks. But if a pin leak does sprout, place the wooden wedge back into the tank and compress the silicone gently until the leak stops. The pressure of the water should help by morning. 

Exterior finishing

Carefully empty the aquarium and give the plywood a good general sanding, avoiding contact with the glass.

Gently remove the silicone which hardened around the glass, but avoid scratching the glass (Fig. 22). Cut from the bottom and from the top, then remove excess silicone until you have a smooth surface.

Lay a piece of oak (U) over one side and mark a pilot hole for the router (Fig. 23). Remove the piece and drill a hole where you marked. I like to label each piece.

After coating the aquarium and underside of the oak plywood with contact cement and allowing it to dry, place 12" x ¼" dowel rods at about 6" intervals along the side.

Place the oak plywood onto the dowel rods. At one end, line up the oak with the side with a little overhang. Remove the dowel and stick the oak to the aquarium (Fig. 24).

Go to the opposite end and repeat the center-and-stick-down procedure. Gently remove each dowel rod with a smooth motion. Do not jerk the dowel rods out, or you could move the oak out of alignment.

Using a roller, securely affix the oak to the aquarium. Repeat this process with the second side.

Adjust your router so the bearing does not touch the glass, using an uncovered window as a guide. Trim the outside edge of the oak.

Starting at your pilot hole, carefully rout the oak out of the window openings (Fig. 25).

The oak on the front edges of the sides should be hand-planed and sanded to a 45° angle. Be careful to avoid removing too much material.

There will be space left for trim on each side of the front piece of oak plywood (Fig. 26).

 I like to scribe a line down both sides of the front so I know where the oak goes (Fig. 27). Drill a pilot hole in the section of oak where the glass will show, and one where the cabinet is open below the tank. Next, apply contact cement to the underside of piece V and to the outside of the front of the aquarium. Allow to dry, then place dowels as you did for the two sides. Lay the oak on the dowels and match it up with the lines you drew. Starting at the top, secure the oak to the aquarium and remove successive dowels.

Rout out the window and cabinet openings. Square the rounded corners with a utility knife.

Cut a long piece of 7/8" x 1" stock in half on the table saw for trim, and glue one on each side of the front oak ply (V). I do not like to fill nail holes, so I take the time to tape the trim to the aquarium after gluing (Fig. 28). Allow the glue to dry for 24 hours.

Carefully plane the trim down until only about 1/16" remains proud of the sides and front (see illustration p.23). If you scratch the oak, you might not be able to repair it. Switch to a scraper to reduce the size of the trim so it is flush with the oak (Fig. 29).

Cut lengthwise 1½" strips from the oak after you measure and mark each vertical side of the three windows. You will have six strips. You may need to label them because you want them to fit as closely as possible.

Make a 45° notch on the end of each piece (Fig. 30). Next, glue and tack the strips into place. Then measure for the six horizontal strips; cut, glue and tack into place.

Plumbing

Gather all your plumbing supplies and become familiar with what they are. It wouldn’t hurt to dry-fit the pieces beforehand. 

One of the 1" male adapters will be attached to a 1" x 15" piece of straight PVC using PVC glue. Drill four holes every ½" along the resulting piece, including the glue end of the threaded piece (Fig. 34). 

The configuration of the return pieces is shown in Fig. 35. Glue only the two elbows together with the piece of 1" pipe (a-b-c), and the threaded end to the other piece of pipe (d-e).

With a straightedge and a grease pencil draw a line along the bottom of the aquarium, tracing the overflow (Fig 36). 

Begin drilling a 15/8"  hole in the corner of the aquarium floor, 1/2" from each wall. Do not drill all the way through from the top side, as breaking through could tear off too much material on the underside and prevent a good seal with the bulkhead fitting.

Drill upwards through the aquarium floor to complete the hole. Once this hole is completed, place the assembled elbow (without the threaded adapter) into the corner where the two front pieces of glass meet, and draw a circle around the elbow to mark the position of the two front holes. Drill these holes using the same method as the first. 

We use standard 1" bulkhead fittings (Fig. 37), regularly used in hot tubs and whirlpools. Make sure the washer goes with the head, not the bolt. It is not easy to hold onto the head of the bulkhead while threading it, so I screw the overflow pipe into it before installing. Line the threaded part of the bulkhead with silicone to ensure a watertight seal (Fig. 38).

Once the bulkhead fitting is in place and screwed in tightly, lay a bead of silicone around the head to further waterproof the whole fitting. Fig. 39 shows all the bulkhead fittings in place. 

Screw the overflow pipe into the bulkhead fitting without using glue (Fig. 40-a). You might need to remove this pipe someday to retrieve an errant fish.

Place plumber’s glue on the threads of each of the two threaded fittings before inserting bulkhead fittings into the return tubes. Screw them in tightly for a watertight seal, which is important here because these tubes hold the electrical cords and water return. Attach the elbows also using plumber’s glue, making sure they fit into the corners of the glass fronts. This will allow them to remain fairly hidden from the outside (Fig. 40-b&c).

Apply a bead of silicone along the two sides and bottom of the overflow (piece Q) and place it in the back corner of the aquarium (Fig. 41). In this photo, background material has already been applied to the overflow. Press to seal. 

Place a length of pipe into each elbow to measure. Each piece of pipe needs to be 1" above the top of the glass. Glue into place. Next, glue an elbow onto one piece of pipe, which will be on the opposite side of where you plan to place the lid. If you are not sure, you can do this after you attach the lid, or just dry-fit the elbow.

The rest of the story

We construct custom lighting and filtration for all our aquariums, but this model lends itself to a commercially available product. Installation instructions will be included. Any good aquarium store will be able to help you select lights, a filter (ask for overflow system, not undergravel) and pump to install in your aquarium. You will need 24" of 11/8" polyvinyl tubing to connect the filter to the overflow pipe and the pump to the return, located at the front of the aquarium, furthest from the wall where you attached the lid. The lights are mounted to the underside of the lid; the electrical cord for the lights runs down the electrical return located at the front of the aquarium closest to where you attached the lid. One power strip, placed inside the bottom compartment, is all that is necessary to power the lights and pump. 

If you are a first time aquarist, freshwater fish are relatively inexpensive. There are hundreds of varieties and they are easy to care for. Saltwater aquariums require a little more attention. We recommend purchasing a dozen inexpensive damsels for the adjustment period, which ranges from two to six weeks. During this time you can familiarize yourself on the care and feeding of more complicated (and expensive) species.

Is Bigger Better?

If you want to build a larger aquarium, you’ll have to consider factors other than floor space and whether you can fit it in through your doors and up your stairways. An aquarium filled with water might be much heavier than you think. In addition to the weight of the aquarium, saltwater weighs 8.3 lbs. per gallon; and then there’s the weight of any sand or coral you add for decoration.

To calculate the number of gallons a particular aquarium will hold, multiply the height by the length and then by the depth of the actual tank portion. Divide this figure in inches by 231, the number of cubic inches in a gallon. 

For example, take an aquarium is 72" long x 22" wide x 32" deep. The calculation for the amount of water it holds: 72 x 22 x 32 = 50,688. The result divided by 231 = 219.4 gal. Now we can calculate the weight: 219.4 gal. x 8.3 = 1,821 lbs. 

1,821 lbs. of water

+ 150 lbs. of sand and coral 

+ 250 lbs., the weight of the aquarium

_____________________

2,221 lbs. total weight

If you divide this figure by the area of floor space the aquarium will rest on, you will get the amount of weight per square inch for comparison; in this case 1.4 pounds. A standard refrigerator weighs about 325 lbs. supported by 1,020 square inches of floor, making it about a third of a pound per square inch.

If your home sits on a concrete slab, weight will not be an issue, but for those with wood sub floors or living spaces on other levels, asking a contractor whether the space will support such an aquarium is advisable. 

Another significant factor for larger aquariums is the thickness of the glass. We had a glass engineer calculate the necessary thickness for the height of the clear cut, annealed glass, and the standard is as follows: 

• for up to 26" of viewing height, the glass should be ½" thick
• for 26"-36" of viewing height, the glass should be ¾" thick
• for 36"-48" of viewing height, the glass should be 1" thick.

If you consider that the fish will only swim 2"-3" above your tallest piece of coral, it might help you determine the desired depth of your aquarium.

And by the way …

If you are in the Orlando, Fla., area, Disney World has several of our custom aquariums in their hotels, and Florida Hospital has one in the lobby. Our favorite Orlando customers were Donald and Robin Royal, formerly of the Orlando Magic. In Jacksonville, we built the aquarium in the Wolfson Memorial Children’s Hospital and the one in the head office of the Jacksonville Jaguars. We’ve shipped completed units to Pennsylvania, Mississippi, Alabama and Chicago.

MATERIALS

WOOD
(2) sheets 1" fir plywood
(1) sheet ¼" oak plywood
(2) 8' pieces of 1" x 2" oak
(2) 8' pieces of ½" x ¾" base shoe
(1) door

ADHESIVES
wood glue
(1) gal. System Three general purpose epoxy
(7) tubes Dow Corning 732 black silicone
(1) gal. contact cement

GLASS
3 pieces of ½" clear cut (no edge work), annealed glass: measure height from bottom of tank to 2" above the opening; measure width on front panel from inside corner to inside corner; measure width on sides from corner to back minus 1"

HARDWARE
(1) box 2" x ½" crown staples
(1) box 2½" deck screws
(1) box 1¾" deck screws
(2) European Hidden Hinges
(1) 24" piano hinge
1¼" finish nails

PVC
10' section of 1" PVC
(3) 1" bulkhead fittings
(3) 1" male adapters
(6) 90° elbows
(1) can PVC glue