Become a Sponsor

Information Pages:
Marine Aquarium
Articles/ FAQs/Index
Freshwater Aquarium
Articles/ FAQs/Index
Planted Aquarium
Articles/ FAQs/Index
Brackish Systems
Articles/ FAQs/Index
Daily FAQs
FW Daily FAQs
SW Pix of the Day
FW Pix of the Day
Conscientious Aquarist Magazine
New On WWM
Helpful Links
Hobbyist Forum WetWebMedia Forum
Ask the WWM Crew a Question
Search Feature
Admin Index
Cover Images


The D.I.Y. Indoor Pond

Building large, economical displays for aquatic life

by Anthony Calfo

Large marine and freshwater fishes can thrive and more readily reproduce in the spacious housing of an indoor pond.

If you participate in the aquarium hobby long enough, you begin to wonder what it would be like to have a really large aquarium. It seems only natural to want to see the “(sea)apple of your eye” swimming in hundreds or even thousands of gallons of water! Reality sets in quickly for most of us, though, and the daunting expense of procuring the aquarium alone remits such dreams to the drawing board, and likely never realized. The sheer cost of raw materials in glass or acrylic to build an aquarium of great capacity will amount to a final cost of several dollars per gallons to construct. And so, some folks begin to consider alternate materials for constructing an aquarium when the notion of an indoor pond inevitably comes to mind. For some displays, this is not even the slightest compromise from a clear-walled aquarium. The aesthetic shift towards viewing the submerged life from above opens numerous doors for constructs, living and non-living, above the water level. Imagine the possibilities with an indoor pond for species variety, if not an outright approach to more complete biotope displays!

This image is available for download. Please contact Bob if you have questions! : Cichlids - Pseudocrenilabrinae, Haplochromis sp (AQ) A high resolution scan of this image may be available for download. Please contact the owner/author if you have any questions! : Algae Rock Plants, Algae-Plants, Vascular Plants, Red  (MANGROVE TONY'S)

Messy feeding reptiles and fishes alike can be kept more successfully in ponds with pond-sized filtration. Technologies from outdoor garden pond husbandry are quite useful here, for their experience with handling high bio-loads from ornamental carp and considerable organic matter.

Aquarists that like heavily populated fish communities or large fishes can find an outlet to continue to enjoy their growing charges with indoor pools. African cichlid enthusiasts can enjoy multi-generation and multi-species colonies of fishes in the widest array or colors, with the comfort of extra space for territories. Fans of big American cichlids like Oscars, jaguars, blackbelts and Uaru can keep and even breed some of these fishes at home finally with enough room. Show-sized marine fishes like puffers, triggers or some small sharks might fairly be housed at last. With a good design, non-piscine aquatics may enter the realm too like crabs, semi-aquatic turtles and other shore life. And let us not forget the options now for horticulture (mangroves, ferns, orchids, etc.) and water features like simulated water falls, dripping pseudo-stalactites, and functioning bogs (AKA vegetable filters). It’s exciting to think that in not much more space than a large home aquarium, we can have a multitude of unique life forms on display, commonly overlooked by most everyone outside of zoological collections.

Aside from the creative freedom and space that an indoor pond gives you, there is the practical benefit that the cost per gallon to build such pools is a fraction of the cost of glass or acrylic aquaria. The best materials for building an indoor pond depend to some extent on the region you live in since shipping costs (freight) make up a significant part of the final cost of any large, bulk consumer good. Resourceful folks have reported on finding a surprising range of options for pond construct: plastic feed troughs in agricultural areas, fiberglass vessels from molds (built or commissioned) in industrial areas, and I’ve even heard aquatic use of the composite-formed liners for (gulp!) coffin vaults! Any of the aforementioned solutions is comparatively inexpensive if you live it the right part of the country where commerce keeps the price of such products competitive. Writing this article for aquarists of the world, though, I proffer a more universal suggestion for building an indoor pond.

Regardless of where you live, common (house-)building materials like milled lumber and flat roof materials (rubber, sheet PVC, plastic, etc.) are likely available, and an affordable option. The images used to illustrate this project depict a 1000 gallon pond built for about $400 USD. At 40 cents per gallon, this is only 10-20% the cost of purchasing the same vessel in glass or acrylic. The basic materials are a good, stud grade of framing lumber, plywood, some old carpeting or sheet Styrofoam for padding (thick layers of old newspaper would be fine instead), and sheet rubber (for outdoor ponds or flat roofs). Assembly will require a few sizes of deck screws, basic power tools (drill, circular saw, spirit level, measuring tape). A sharp wood chisel or coarse sand paper will come in handy for taking care of rough wood edges. Scissors or a knife will also be required for trimming the liner to size, unless you can chew like a beaver. At length, nothing employed for the construction of this pond is uncommon in a household big enough to hold an indoor pond to begin with.

Where do we start? With imagination! It is the single most important item that you will bring to the project. Sit down in the space that you intend to place your pond and simply visualize and spend some time contemplating the possibilities of the display, both above and below the water. Some aquarists take a traditional route and keep the pond very simple in both construct and plumbing with not much more to speak of than a sound, plain walled pond upon completion. Others may wish to employ through-wall bulkheads for drains, plumbing, electricity, or submerged lights. Consideration of track lighting, power supplies, or even remote filtration (placing the serviceable hardware in another space or room behind, beside or below the pond) could also be issues worth exploring.

An address of such ideas and possibilities for the ancillary features of an indoor pond would require volumes of space to even begin to discuss adequately. I have worked for some years professionally designing and installing ponds for private aquarists. My dear friend and colleague/co-author Robert Fenner has done this work very well for decades. His free-content website details some of these wonderful aspects of pond-keeping among a plethora of other topics of aquarium hobby, science and business in actively archived articles, images and FAQs. Please take the time to explore this website for ideas and inspiration, and feel welcome to contact us and our crew with more specific questions about polishing your dream pond. For now, however, let us focus on the simple construct with an illustrated, step-by-step tutorial.

Step 1: Lay out all necessary tools and materials within comfortable reach. You will build the pond in place and not move it from remote.


Step 2: "Measure twice, but cut only once" as the saying goes. You should pre-cut as much lumber as possible in preparation for assembly.


Step 3: A good friend and helping hand is priceless, and makes passing the time more enjoyable on the project.


Step 4: Install all new service features (water supply lines, electrical outlets, light fixtures and switches, etc.) before the pond is built, or at least before it is filled. It is easier and safer to do such work in and around a dry pond. Note: be sure that all electrical lines are Ground Fault protected (with proper GFI switches or breakers).

Step 5: Begin the pond form with vertical side walls. Carefully measure and mark positions for horizontal bracing. See the images below for the use of framing lumber (studs) as stabilizing ribs to the pond structure. Take the time to pre-drill pilot holes and screws for securing the bracing on the outside of the pond.


Step 6: Your first finished vertical wall will be the simple sum of a pre-cut sheet of thick plywood plus bracing studs/ribs cut with mitered ends. Be sure to use veneer plywood (marine grade when available) and not particle board (glued sawdust) or pressed wood (glued wood chips) for this project, for durability and strength. Common, construction grade plywood of ½ - 3/4" thickness will be fine for ponds less than 4' high or 8' long. Larger vessels may require thicker sheet and bracing lumber, if not  the use of engineered bracing like a four-sided capture or some such (welded metal banding as straps or a collar).


* Very tall or wide ponds (over 3 - 4') may require additional bracing beyond the fixed ribs. This picture depicts German aquarist Daniel Knop's magnificent reef aquarium (well over 1000 US gallons) from above with discreet reinforcing rods to prevent deflection of the vertical walls. On ponds, aquarists can use a variety of materials to accomplish this goal. Simple solutions run the gamut from steel cable fished through plastic hose for protection, to triangular caps on the corners. Skilled hands can instead weld steel (to be epoxy coated later) or rivet anodized aluminum (use stainless steel rivets to resist corrosion) in rods or straps tied into a collar at the top of the vessel.


Step 7: With two vertical walls assembled (bracing lumber screwed and glued [optional] into place), the opposite side-wall bracing can be used tie three walls together. It is here that you will really appreciate the time spent to miter the corners of the bracing lumber.


* You can glue mitered joints with aliphatic resin - AKA wood glue - or simply screw them together with quality deck screws (fasteners made for outdoor construction and weather resistance). Regardless, such joints are stronger, easier to butt, and aesthetically more attractive

Step 8: Securely install all matching ribs for the first opposite wall.


Step 9: Next, set and screw that (interior placed) vertical plywood panel into position.


Step 10: Throughout periodic stages of construction, be sure to check the plumb of your work. You may want to strategically allow a very slight slope to one side for future drainage and water pumping. In some situations, a false floor to the pond is now built for an actual floor drain (seek such bulkhead fitted drains with seals from a pond or swimming pool supplier) or to house plumbing or filtration components. Other folks may plumb features (lights, water, electricity, e.g.) through the pond to the next floor of the house below. A (ply-)wood floor fastened to the side walls lends considerable support to the structure and is encouraged. The pond depicted here is in the basement/ground floor of a home and will be taking advantage of the naturally cool, stable ground temperature conducted through the concrete foundation without employing a wooden floor.


Step 11: Finish securing the 4rth-panel ribs and plywood wall. Important - it is necessary to countersink all screws (or center punch nails) on interior surfaces that the liner or padding will come into contact with. A sharp woodworker's chisel will level any burrs or irregularities in the wood assembly.


* To fill the corners of your pond's form, rip a square piece of milled lumber diagonally to make a symmetrical triangle (a table saw works best for this). Split here is a standard US 2" x 2" (5 cm x 5 cm) piece of blocking lumber.


Step 12: Nearly finished, you should pad all interior surfaces that your liner will contact. Find something inexpensive or recycled for the purpose. Old carpeting works well here; check with neighbors the day or night before municipal waste pick up. Insulating Styrofoam sheet is affordable too (pictured here in pink color). Aquarists have also used thick layers of old newspaper for many years. Note: do not secure padding with any sort of fasteners! Screws, tacks, nails or other like fastener may puncture liner if enough pressure is applied from the inside (falling rock, walking feet, pressure of water, etc). Simply cut and set padding in tightly (snug fit) or glue lightly (contractor's caulk).


Step 13: When the pond is framed and padded, you are ready to size up the liner. Lay it out on a clean, flat surface.  The garage floor or driveway may be safe for this purpose. Avoid walking on the liner at this time. Without padding or support behind the liner, a stone or other hard foreign object poses the risk of puncture under the weight of a man's foot. With the liner fully unfurled, you will measure and cut it to size. The dimensions of the cut liner will be the total continuous length of a side = 2 x height, plus length, plus 2 x width of cap plus a bit extra for folding and pleating. For example, if a pond is going to be 6' square by 3' deep with a .5' wide ledge, then the liner must be cut at least 13' x 13'. We arrive at the measure of 13' per side by taking the length of the pond (6') plus enough liner to run up either side (2 x 3' height) plus the overlapping liner that caps the pond's edge (2 x .5'). But again, please cut the liner slightly larger (10-20% minimum) to allow for comfortable folding and pleating in the corners.


Step 14: Drop the liner loosely into the frame, but do not tack, nail or tie down any part of it until you fill the pond! The liner will pull and shift slightly as it fills and any fastener applied to the top edge will likely tear away and damage the liner. In fact, one or more people will need to be in or around the pond constantly as it's filling to make certain that the liner lays flat and unwrinkled on the bottom, while gently pulling and tugging the upright sides to make tidy, folded pleats in the corners. Do not allow any air pockets to form underneath bunched or wrinkled liner… especially on the bottom. These are vulnerable to tear or puncture, as mentioned already.


Fill the pond to its highest point. When the liner is laying flat all the way around with clean pleats and folds, then trim excess liner away. Simply weigh down the top edge of the liner (my preference) if you do not lightly tack it. Be sure to cap the top edge to protect the liner from wear or damage in time. Some folks have access to the relatively new "plastic" lumber which is intrinsically colored and requires no painting or sealing like wood and is quite ideal for water's edge applications. Stonework is also a natural and handsome finish for your pond's edge. Most aquarists prefer to apply a cap that hangs over the edge enough so that the liner is not apparent when the pond is full.

Finally: the finished pond is now your blank canvas to adorn and personalize! The exposed bracing lumber and panels might be painted. Some folks prefer to face the pond with a veneer (wood or concrete composite) for decorative ceramic tile. Perhaps you can integrate a theme for your pond into the facade, like nautical artifacts (fish net, curios, sailing instruments), or natural rock of the simulated biotope (calcareous tufa, fossilized coral, volcanic lava, etc.). Use your imagination.

I hope this introduction to indoor DIY pond construction has offered some information of merit. Interested aquarists are encouraged to visit local garden centers for advice, books and pamphlets on outdoor pond construction and maintenance. Some guidance on filling a pond (making pleats with liners) and installing filtration components (bulkheads, drains, water features, etc.) is highly recommended as part of your preparation and research before building a pond of any size. Be assured that outdoor garden pond-keepers share many similar interests and challenges as indoor pond-keepers. Take advantage of lessons learned by them and enjoy their wisdom and fellowship.

General Parts List

Tools and materials to make indoor ponds up to 1000 US gallons (3785 liters)

[costs are approximates and vary by region]


3 – 4   4'x8'x1/2" Plywood sheets…  $25 per  [upgrade to 5/8" or 3/4" thickness, and/or marine grade if desired] $75 - $100
15 – 20 2"x4"x8'   Framing lumber ("studs")… $2.50 per  up to $50
2 - 4 2"x2"x8'   lumber… to be ripped diagonally for seams $2 per up to $ 8
5 lb. All-weather Deck Screws [nails less expensive/weaker] $ 20
Variable  Styrofoam or cheap carpeting to pad interior shell [used carpet/old newspaper free instead - contractor's sheet Styrofoam quoted here ] $15 - $30
Variable Liner: pond liner, roofing rubber (aged, or rinsed new), PVC sheet (40 – 60 mil) [Highly variable cost per region, material and size – here we have quoted a pond liner purchased at a retail local pet store. Expect to pay less than $20 per linear foot of rolled product up to 20' wide.] $200

Recommended Tools:

  • spirit level

  • measuring tape

  • drill/screw gun

  • saws (table/circular)

  • marking pencil

  • coarse sandpaper/chisel

  • center punch (if nails are used instead of screws)

  • razor/knife

  • hammer


  • motivational music (Neil Diamond and AC/DC compilation disc… quite special J)

  • tasty wine or beer

  • 12 lbs of pork rinds (source of carbohydrates to fuel good work… among other things)

Anthony Calfo is an active writer living in scenic Western Pennsylvania . He is an author for Reading Trees publications and (aquarium science). Please feel welcome to make contact at 

"Book of Coral Propagation", Volume 1(2001) by Calfo

"Reef Invertebrates" – Natural Marine Aquarium series volume 1 (2003) by Calfo and Fenner



Dawes, John (1989): "Book of Water Gardens ", T.F.H., Neptune City , NJ U.S.A.

Liner/Wood Ponds on WWM:

Related FAQs: Above Ground Pond Liners

Related Articles: Liners for Above Ground Ponds by Bob Fenner, Liners in Pond Construction Overview



Featured Sponsors: