Building an Indoor Pond

To build an indoor pond had been a long time dream of mine. I call it a dream because it was not something that my better half would have approved under normal circumstances. Also, our house was not so big as to hold a real nice little pond (like a few I saw when doing some research on indoor ponds). However, I did have a nice sized basement, though already packed with game and gym apparatus, it still had enough room. I spent days wondering if this would be a good idea. One of my primary objectives was to build something to transfer my two Japanese Kois. They had been with me for about six years in a 135 gallon aquarium and were getting too big for it. I had two choices - to build a pond in my backyard or to build something indoor. The third option presented to me by my better half was by far the worst – to get rid of the fishes. No way! They had become like my children and I wasn’t about to let them go.

The choice that looked the best initially was definitely building a small 1000 gallon pond in my backyard. I had a relatively small backyard but yet big enough to create a 1000 gallon pond. The problems were two fold. First of all, I needed a way to tackle the freezing winter. Secondly, I would need a special setup for the pump and filter. It was possible to solve both but not very cheaply. After thinking hard I decided to move out of this option and go for a simpler and cheaper indoor pond option. That way I won’t have to worry about having an electric line in my backyard and spend extra electricity to keep the pond going in the winter (for gas exchange a small passage needs to be present all time).

After careful consideration I chose a corner in my basement that was holding an air hockey table. Kids sometimes played it so I needed to find a new place for it. That was easy.

However, there were multiple other important factors that I needed to consider.

• How big the pond should be?
• Would the basement be able to handle the huge load that the pond would put?
• What kind of pump and filter do I need?
• What about humidity?
• How costly was it going to be?
• And finally, exactly how to build it?

One of the common criteria for all my projects had always been to keep it low cost. My better half almost always categorized my projects as ridiculous. The only way to pacify her was to keep them easy on the wallet. This had not been easy over the years. Cheap solutions do not always work better and often not very pleasing to the eyes. But as long as the purpose served I was okay with it.

If you are interested in doing something like this then please pay good attention to all the details from here. I’ll answer each of the questions stated above one by one.

• How big the pond should be?
• I was aiming for a 500-600 gallon pond. The corner that I was targeting was 8 feet long and 4 feet in width. I settled for a size of 8 feet by 5 feet and 2.5 feet in depth. With 2 feet of water the total volume would roughly be 600 gallon, give or take.
• Would the basement be able to handle the huge load that the pond would put?
• Basements are usually built on a well drained bed of gravel or crushed stone by pouring concrete.  It should be able to handle large amount of load. In my case the calculation came up to be ~6000 pounds on a 40 sft area; 150 pounds per sft; little over 1 pound per 1 square inch. This is really not much of a load. [Every situation can be different. So, please take due diligence to ensure that the load can be bore by your floor. It is probably a good idea to do a strength test on the floor if you are in doubt. I would not suggest building a pond on any other floor than the basement though]
• What kind of pump and filter do I need?
• There are many types of pump and filter. I settled for something that would turn the water at least once an hour. I assumed I’ll have only my two Kois (9 years and 6 years old) and some gold fishes. That kind of filtering and water movement should be just fine. I spent about $300 on both.
• What about humidity?
• This is where I really got bogged. I read and read. Put my hygrometer (humidity measuring instrument) in the basement for several days to find out the average humidity (this will vary based on season being high in summer and low in winter).  
• I assumed that the pond would increase the humidity by additional 10-20%  based on how much water movement was in place and started to inquire what kind of negative impact that may have on the house. The findings were obviously not very encouraging. So, I decided to buy a dehumidifier. Extra cost but had little other choice. Another thing that I also considered was what could be the impact on the section of the first floor right above the pond. Over time the extra humidity can damage the hardwood floor. Fortunately for me I did not have hardwood floor on that specific part. Nevertheless I made a mental note to regularly check after the pond is built for any impact.  
• And finally, exactly how was I going to build it?
• Okay, now the main part. How to build one? I saw several ways people did it. One of the most popular ways is to use wooden structure. However, water is very heavy and unless built properly the structure could fail over time. So I needed a good, solid design.
• I know little about woodwork. I continued to look into the web and finally found something that I could work with. This is how I did it. You can try various variations of this but this would work fine. I do not have the original design as I did it almost a year ago but this is something that is fairly close.
• Once the framework was completed I used carpet and cloths at the bottom and specially at the corners before laying down the pond liner. After this the rest was really about filling it up, putting in the pump and filter and cover the open parts of the frame with nicer looking stuff (you can get pretty creative in this part). I did not care a whole lot about the look but if you don’t mind spending some more you can do all kind of stuff.

 Use 6x6 s for the four corner stands; connect them with 2x3 lumbers (pink). There is no one way of doing this . Just make sure the frame is very sturdy and doesn't move if you shove it lightly. In the outer side and inner side use strong, thick plywood (brown). The blue section is the part where you would put water in after  laying off the pond liner. 

I built it all alone from scratch in my basement over next 2 to 3 weeks after work. Bought whatever I needed. At the end things came out to be just fine. I wish I had taken some pictures but as always it is always an after thought. Here is the finished product.

So, I have the pond for more than a year. Everything seems to be going great. Couple of issues that I noticed:

• Humidity: It is not a problem in winter but in summer if I do not use the dehumidifier the humidity goes as high as 80% in the basement.
• Good water movement in the pond is a must otherwise algae starts to form on the inside walls of the pond. I use only a 30 watt florescent light for 5-6 hours at night. No direct sunlight reaches the pond.