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Hi All,
I have been doing a lot of reading of the forum; a wonderful resource for those of us "just starting out".
A couple of years ago I was doing some trekking in South America and was letting my mind wander. I started thinking about my garden back home and thought that if I could raise my veggie beds and place some sort of tray/saucer under there, I could capture the water that had already done its job watering the plants and recycle it. The water would be clean after being filtered by the soil, so I thought it might be good to keep some fish in that water. Their waste would feed the plants, the plants and soil would clean their water -- harmony. When I got home I started by building a small scale project and it worked quite well. I needed to ramp it up a bit so I started to do some research; imagine my surprise when I learned that my "original" idea had been used by thousands of others for many years -- aquaponics!
Anyway...
My experimental systems have grown and changed in the last 12-18 months; plumbing has changed, capacities increased etc. I love to tinker, so this is the perfect hobby project for me. As nearly everything is scrap/junk, the price is kept very low even for modifications, which is very important for us in these "tough economic times."
At the moment, we have a 500L fish tank (below ground - it is built into our backyard "water feature"). In that pond I have a submersible pump (allegedly, according to the manufacturer, 3500L/H at 0m, about 1800L/H at 1.3m). The pump output is split; approximately 40% is pumped up into "the system" 1.3m above the pond surface when full, the remaining output is sprayed back onto the water surface to aerate and agitate the water. The "system" has a coarse particle filter to take out some of the solids, then four 3 metre lengths of 100mm PVC pipes (pseudo-NFT tubes) stacked vertically which gravity drain through a slow-drain-standpipe from level to level. Under the last pipe, I have a 100L bucket partially filled (I need to get some more) with expanded clay balls (a small grow bed) and another coarse filter through which the water finally passes as it drains under gravity back into the fish tank. When the system is full, it draws about 25% of the fish tank capacity, leaving 75% for the fish. The pump cycle is on for 15 minutes off for 60 minutes during daylight hours. An air pump runs periodically overnight to aerate the water for the fish. We are very concerned at the cost of running our system. We have 1.2kW grid connected solar power but this does not mean that we can afford to run pumps and aerators continuously all day and night.
The trial systems started with a few goldfish (which have grown dramatically!); as the experiments continued more goldfish were added until there 14 of them. About 4 months ago I introduced 6 slightly-larger-than-fingerling rainbow trout to the system. The pond was covered with 25mm mesh to keep the cats out, but what I didn't expect was the local crows to be able to pluck out a fish through the mesh, but they did! We weren't sure what had happened when one day there was dead trout on the lawn some 3m from the pond, and then a few days later I watched as a crow took the second fish. We now have 10mm mesh over the pond and have lost no more fish (except when I accidentally "speared" one smaller goldfish whilst doing some cleaning!) The four trout are just about ready for harvest, the largest is about 800g or so (they're so hard to weigh accurately!) the others are only slightly smaller. Yesterday we added another 25 slightly-larger-fingerling rainbow trout, hopefully these will be ready by the end of the year? So right now I have:
4 almost ready for harvest rainbow trout,
25 small rainbow trout, and
13 goldfish of various size.
In the PVC pipes, 83mm circular holes are cut at about 130mm intervals so we can insert 24 mesh cups per 3m length (lesson learned: measure twice cut once! We wanted 25 cups per length but mis-measured and only ended up with 24 in the first length, so for symmetry had to make the same cuts in the remaining lengths.) This means we have 96 plants growing in the pipes. We have had tremendous success with:
celery,
tumbledown tomatoes,
parsley,
silverbeet,
spring onions,
strawberries,
coriander,
basil,
lettuces (all varieties tried grew well, except iceberg which failed to form heads),
leeks,
beans (except the chooks got to them first and ate the whole lot!)
and a few other items which don't spring to mind just now. (lesson learned: write everything down.)
Things that didn't work so well included:
spinach (planted in winter they survived but didn’t grow),
broccoli (bolts straight to flower),
cauliflower (still growing very slowly),
cucumber (planted in summer, the inside parts of the plants grew too fast and split the slower growing outer membrane of the plant!),
miniature globe eggplant (fruit just won’t ripen),
broad beans (survived the cold as almost leafless stalks),
okra (took off like a rocket for a few weeks, then did absolutely nothing!),
and a few other items which don't spring to mind just now. (lesson learned: write everything down. Déjà vu, it must be true!)
After doing some research we learned a few things about pH, EC, temperature etc. We bought an electronic pH meter and electronic electro-conductivity (EC) meter and religiously measured these parameters twice daily. The max water temp at the end of last summer (start of monitoring) was about 19.5C and the min in winter (assuming the last of the cold weather has passed) is about 14.0C I was adjusting the pH trying to maintain a level of 6.5-6.8 but the system had other ideas and liked to settle itself at about 7.3-7.5 I gave up spending money on buying acids etc to bring this under control and left it to do its own thing; the plants and the fish seem happy enough. As for the EC, we had advice we should have a level at about 1.5 (whatever units) but our system was constantly less than this at about 0.3 I kept adding small amounts of a liquid hydroponic fertiliser which made the plants happier and the fish didn't seem to mind; it's expensive stuff though so I generally leave the EC at not less than 0.5. A doctor friend sourced some dipsticks for me to measure nitrites and nitrates but the readings were erratic at best (I don't how reliable these things are supposed to be, but if this is the "medical standard" then the next time I go to the doctor and he asks me to pee into the jar... there is no point.) We didn't get a liquid test kit, baulking at the cost, so we have never accurately measured the nitrite, nitrate or ammonia levels.
Things seem to be running ok, but I am sure they could be better?
The fish pond is a "coffin" tank measuring about 1.95 x .52 x .45 so the fish can only swim laps from end to end; does this affect the quality of the fish? Does a fish swimming endless laps in a stream around a circular pond would result in firmer, fitter fish? Better eating?
I have never added salt; should I?
I feed the fish only once per day, but I have read of others feeding theirs 6 or more times per day. Is there a consensus about how much, how often?
The water often goes green and stays green for a very long period. Once it cleared up by itself, but usually after 8 weeks or so I get annoyed enough to replace the water with clean fresh water (which ends up going green again in about a week). What causes this? Can it be rectified? Could it be the hydroponic fertiliser? What needs to be done so that I don't need to add this?
I would like to be able to grow barramundi in the summer but I don't want to have to install water heaters (I am considering installing an old solar hot water system panel, or some black polypipe akin to a swimming pool heating system). We have been "reliably" told the ideal water temperature is 24C?
Although we are seriously looking at a BYAP system (3000L cylindrical tank and at least two 500L grow beds to add to the existing pipe-work and 500L pond) this will only be when the work situation picks up again and we can afford such "luxuries". What other recommendations do others have for now? (At no/low cost?)
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One thing I have experimented with, removing the expanded clay balls from the mesh cups once the roots of the plant have successfully anchored the plant. I started doing this when the celery started going nuts as the roots and the balls were expanding in the cups making them almost impossible to remove from the PVC. With the balls removed, the plants still grow well and there is less trouble with over-expanding the cups. This experimental method has worked well with celery, spring onions, silverbeet, basil and a few others. Logically, it shouldn't work in a NFT system as there is no medium other than the roots for the "NF", but it does work.
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I look forward to hearing from others and sharing their experiences.
Scott
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Backyard Aquaponics
Well done.
