Now that the aquaponic system is all plumbed up and leak tested, it’s ready for the last few steps so I can start adding fish and plants. The first step is to get a baseline reading of the water – the critical measurements being pH, ammonia, nitrites, and nitrates. For a properly running system you want a pH to be around neutral (6.8-7 is a good range), ammonia and nitrites at 0, and nitrates around 20 ppm. If the nitrates are too high it is bad for the fish and too low won’t provide food for the plants. One of the most popular kits for water measurements for aquaponic systems is the API Fresh Water Master Test Kit. The readings were all good since the water was new, the pH a little high but as expected for a new fill up and nitrates were 0 since there hasn’t been any activity into the system yet.
Now that I had a water baseline, time to start adding media to the grow beds. I’m using expanded clay since I got it as part of the deal with the system, there are less expensive alternatives if you are starting from scratch. While adding them it was interesting to see that some sink right away and some float (bed to the right).
With the media added I was curious what the water readings would be after running for a day. The media had been used in a system previously so what effect did this have on the water? To my surprise and delight, the ammonia and nitrates were still zero but nitrates were at 30 ppm. This being the case, I went ahead and dropped some starter plants in to take advantage of it and get a jump start on balancing everything out. I also added some filter material into six inch net pot cups to act as mechanical filtration from the fish tank.
Next, I added an aerator to the system. It’s debatable whether additional aeration is needed with all the water splashing around already but it certainly won’t hurt. For this I selected the Aquascape 75000 Pond Air 2, primarily because it is the right size but also since I have had good luck with a larger Aquascape pump that has been running in my larger pond. For just a few extra dollars you can get the extended warranty through Amazon, in my opinion it was worth it. This aerator came with 2 separate air stones and plenty of tubing. The first stone was placed in the sump.
The second air stone was placed in the fish tank, and the aerator itself was put under the fish tank on the ground. A future project will be to make a weatherproof box to contain all the electrical items and a backup power supply.
I also added a 250 watt heater to the fish tank. I’ll add a second one before winter next year but for now I think we are past any really cold days. I’ve chosen to stock the tank with Tilapia which can die out if the water goes below 50 degrees so it will be important to have some redundancy. Once the heater and aerator were set up the Tilapia were placed in the tank, around 35 total of various sizes so they can be harvested at different times.
Now there’s fish and some starter plants in the media beds, time to build a raft for the remaining grow bed. The board of choice is the DOW 2″ Blue XPS styrofoam board. If you can find it locally it will be a lot cheaper but unfortunately I couldn’t and couldn’t order it from any of the big box stores. The nice thing about the way i got it was that it was 2 smaller pieces so cutting to fit wasn’t very hard. I started by trying to use a foam cutting tool (looks like a soldering iron) but that turned out to be too slow and didn’t make a very nice cut. A battery powered circular saw was the better choice.
After the initial fitting the next step was to cut holes for the fill and drain. When drilling holes using a hole saw make sure to extend the center bit out so it pokes through the other side.
Most hole saws aren’t deep enough to go through all the way so you may have to flip the foam over and finish from the back side. Having the center bit poke through helps with alignment.
Next, measuring and cutting holes for the net pots. I used 3 inch pots and from research it seems having 8 inches of spacing was the minimum suggested. Here’s a look of the layout I used, no actual measuring as I figured it didn’t have to be perfect.
Once you have the layout, just use a mark the locations with a sharpie. To cut the holes I used a 2 7/8 hole saw that I got locally at Ace Hardware. The big box stores didn’t carry this size in stock. I tested using a 3 inch hole but the pots weren’t very tight.
This step is optional but I want the system to look good and hopefully extend the life of the foam . I painted the foam with a white latex exterior paint, one coat over most of it and 3 coats on top. I let this dry for several days before risking putting it in the system.
Last but not least for now, I wrapped the raft bed and fish tank with black plastic. This should cut down on algae growth. My original plan was to build wooden frames around the tanks but when pricing the cost of lumber that idea took a turn. The plastic will work for now and I’ll keep an eye on Craigslist for some free scrap fence panels or pallets that can be re-purposed for this.
One final picture, a closer view of the raft once installed.
Next I’ll be adding plants to the system. As time and materials allow, I’ll build nicer covers, a protective cover over the fish tank to keep birds and animals out, an automatic fish feeder, a backup power source, a box to house the electrics, and a shade cover over everything.
I’ll post monthly updates on how this system is doing, but for now I consider it a success. Happy planting!