A mature Aquaponic system generally only needs minor additions of Iron and perhaps Potassium, Magnesium or Calcium. However, variations in the PH of the source water, the quality of the fish feed, PH adjustment method, and media used in your grow beds can all affect the nutrient balance.
There are several ways of knowing various levels of the key components of your system. The most complete and accurate is to send a sample of your system water to reputable water quality lab for testing on a regular basis. However, there are many individual testing kits for various elements as well as several complete kits. In this article, I review the usefulness of several such kits.
LaMotte - Hydroponics Test Kit AM-41 Code 5406Retail Price: $566.00 Tests include pH (4.8–7.6), nitrate nitrogen (5–200 ppm), ammonia nitrogen (1–8 ppm), phosphorus (3–30 ppm), sulfate (0–200 ppm), calcium (0–2,000 ppm), magnesium (0–1,200 ppm), potassium (0–250 ppm) and spot detection of iron at .25 ppm. Kit and reagent refill includes enough reagents for 50 tests per parameter. Manual and 75-page handbook included. Kit weighs 15 lbs, refill weighs 1 lb. This kit was developed for use in Hydroponics. The single biggest challenge in testing an Aquaponic system is that our normal levels are substantially lower than that of Hydroponics. Hydroponic nutrient levels are often 10-100x greater than that in Aquaponics.
1) Potassium-The instructions suggest diluting the sample 5 to 1, then it dilutes again 2 to 1 or a total of 10 to 1 and then you multiply the answer by 5. I received no reading. So I skipped the 5 to 1, still no reading. So I redid the test with no dilution (multiply the answer by .5) and it showed the system is running about 5ppm Potassium. note: my ph runs high, so I don't use calcium or potassium to buffer ph, but I still supplement some to insure enough for the plants. The UVI Basil test ran 30-86ppm, so I'm definitely low, and that may account for some of my older tomato leaves that die. I repeated the test at full strength, and got a reading of 10ppm, slightly higher then the 5ppm before. The reading is taken by inserting smaller container in the larger container which has a black dot on the bottom and is calibrated on the side, you lower the smaller tube, looking down into the tube, until the black dot is obscured by the cloudy water, then read the ppm at the water level. My system with a little supplement runs 10-20ppm. Another commercial system I know of runs 200-400ppm because they use Potassium to buffer their PH.
2) Iron - unfortunately the test only tests that there is .25ppm or greater, it doesn't test the actual level, and as the water color shows, I have at least .25ppm. I've tried several other individual test kits for Iron and find that this is one of the more difficult elements to measure. In practices, the plants tell me when they are low in iron. UVI has levels of 1.3ppm, another system .5-5.0ppm. This test kit would show a positive result for all of the above, and therefore is not of practical use for us.
3) Calcium-Magnesium test. This one still has me stumped. It reads zero for both these chemicals and that can't be right. I emailed lamotte, and they say I'm doing the test right. The first part of the test is a titration test for the ppm of BOTH. The problem is that it reads ZERO of both. I emailed the tech support and they confirm I'm doing the test right. It reads from 0 to 500ppm on the titrator. I mixed a solution of tank water and a few drops of liquid calcium and epsom salts (magnesium sulfate). then tested with this sample. The liquids do change color to red and when the titration is added changes back to blue. (reminds me of my dissolved oxygen test kit.) So it does detect the presence of calcium and magnesium, but either my levels are none existent (I supplement probably 2 tablespoons of calcium nitrate weekly and the same of Epsom salts), or they are so low,they are below the level the kit can test well. I went ahead and did the 2nd part of the test which just tests for calcium separately. The reagent for this step solidifies at temperatures below 68 degrees, so I had to warm up the liquid first. It did detect levels of calcium, but given the problems with the first part of the test, I did not trust the readings. I since purchased additional test kits (reviewed below) and it seems the levels in my system are very low, and this kit does not test as well at low levels.
4) Sulfate - I ran this test several times. You put the sample in a box of comparisons, but in this case, it's not color, its how clear a dark line appears. As near as I can tell the level is between 150-200ppm. If that's true, it's way high. The UVI basil study only ran 10-24ppm. My solution is a white cloudy, the comparator is a more gray and I find it very difficult to see differences in the black line behind the solution.
5) PH - This is a standard reagent based test. I ran the test just to see if it came up with different result than my other kits. My other test kit shows about 7.0, The electronic meter I have shows 7.0, this showed 7.0-7.2 (comparing colors in any of these tests can be tricky.) - (A man with one watch always knows what time it is, a man with two... well.)
6) Nitrate Nitrogen - It took me 3 times to get this one down. I found you have to dilute the sample 10 to 1 (the kit comes with de ionized water for this purpose). Then the samples from my system run 15-60ppm nitrate nitrogen. This tends to be higher than the other standard aquarium test kits. The reading is taken by placing the test tube in a comparator box, and comparing the color of the sample to fixed color samples. This test takes 12 minutes to complete. UVI's data shows their system runs 10-50ppm.
7) Phosphorus - This is an easy test to do. The instructions call for the sample to be diluted, but to get a reading I used the sample at full strength, no dilution, then divided the result by 2. it shows readings of 20-40ppm, again by comparator box. The UVI system runs 15ppm.
8) Ammonia Nitrogen - Again it took several attempts to determine the dilution, or in this case, NO dilution - The test in all cases showed Zero ppm Ammonia Nitrogen. The reading is taken using a comparator box. The UVI system runs .25-2.0 in the fish tank, with levels at or near zero after the water has gone through the raft tanks.
All-in-All this is an expensive kit that is not necessary for most hobby systems, and is calibrated for higher level nutrients found in Hydroponic Systems. A selective purchase of some of the individual kits below may be more economical and useful.
LaMotte Dissolved Oxygen - Model EDO Code 7414, also Code 5856
Retail Price: $49.95
This kit provides an inexpensive alternative to a dissolved oxygen meter. Testing takes 5 minutes. 0 to 10 ppm (mg/L). Note: These tests may not give accurate results when used with ammonia-reducing chemicals. In my opinion this is one of the critical test kits for any aquaponic system that intends to maximize production as sufficient oxygen levels are critical to the health of most fish, and especially the more sensitive trout species. There are two versions of this test kit, one uses Sulfuric Acid powder, the other Sulfuric Acid liquid. The liquid is easier to use, but cost more to ship due to hazard materials charges. Both yield the same results. The test takes just a couple of minutes to complete and are very accurate. This test is highly recommended.
Lamotte Nitrite Nitrogen - Model SL-LNR - Code 3352
Retail Price: $77.95
Nitrite Nitrogen is an intermediate compound formed in the oxidation (nitrification) process of ammonia becoming nitrate. Nitrite can become toxic in recirculating systems. Nitrites interfere with the ability of the fish's blood to take up oxygen (levels as low as .2 ppm can cause "Brown Blood" problems in many species). Testing takes 5 minutes. Range: .05 to .8 ppm.
This kit works well, but is expensive overkill as the standard aquarium test kits produce adequate results for a fraction the cost.
LaMotte Ammonia-Nitrogen Test Kit - Salicylate Method - Code 3304
Retail Price: $74.25
The test kits measure total ammonia. Total ammonia consists of both nontoxic NH4+ (ionized) and toxic NH3 (un-ionized) forms. The proportion of one to the other is variable. The toxic form increases in proportion as the pH and/or temperature increases. Ammonia builds up in the water primarily by the metabolism of protein (nitrogen). About 10% of the protein fed to fish will show up as ammonia in the water. This test takes 21 minutes to complete.
Again this test kit works well, but is overkill, the standard aquarium test kits are normally adequate and much less expensive. There is one exception to the above. If you have treated your tanks with a low level salt or have a treatment tank that has higher levels of salt, then the standard tests are not accurate and a Salicylate method test is needed.
Lamotte Iron In Water Model SL-P61 Code 3318
Retail Price: $71.10
LaMotte Iron Model P-62 Code 7787
Retail Price: $92.10
Model SL-P61 measures a range of .5-10ppm, Model P-62 measures a range of 0.05-1.0 ppm. I found that my system levels were very low and the P-62 model was required to get accurate readings. This is not a must have test kit, but is useful as Iron is one of the deficiencies found in may aquaponic systems. The SL-P61 kit uses a color slider to compare the color of the sample to a set of color screens. the P-62 kit is a comparator box and you move the sample from slot to slot to match the colors, both are easy to use and take just a couple of minutes to complete.
LaMotte Total, Calcium & Magnesium Hardness Model PHT-CM-DR-LT Code 4824-DR-LT
Retail Price: $55.25
LaMotte Hardness Low Range DRT Model HCM-DR Code 3037-DR
Retail Price: $46.70
The total hardness of water generally represents the total concentration of dissolved calcium and magnesium ions. Although closely related to alkalinity and the buffering capacity of water, high alkalinity may not always indicate high hardness.
Hard waters (above 150 ppm) are generally more productive for fish than soft waters. The typical range for aquaculture is 50 to 200 ppm. Both tests take about 2 minutes. The total test kit measures from 0 to 200 ppm, the low range test is from 0-10ppm and is not useful in aquaponics as the range is to low, furthermore, it only tests for total hardness, where as the total test kit will give you a reading for total hardness, calcium ppm and magnesium ppm, which is much more useful. This is not a must have test kit, but is useful in testing and diagnosing certain plant deficiencies.
LaMotte Alkalinity Model WAT-DR Code 4491-DR
Retail Price: $29.99
Alkalinity refers to the quantity and type of compounds present in the water that shift the pH above 7.0. Water with high alkalinity tends to be more strongly buffered. Buffering will reduce the tendency of the pH to shift. Add sodium bicarbonate to increase alkalinity (buffering capacity) and calcium chloride for hardness. Testing takes 2 minutes. Range: 0 to 200 ppm. My system runs 50-250ppm.
This is another simple test that takes just a couple of minutes to complete. Alkalinity is not generally an issue in aquaponics and therefore this test is not generally needed.
Lamotte Carbon Dioxide Model PCO-DR Code 7297-DR
Retail Price: $46.45
Carbon dioxide (CO2) is present in water as a dissolved gas, like oxygen. High CO2 can stress and even kill fish. It also forms carbonic acid, which lowers the pH. Testing is by titration and takes 2 minutes. 0 to 50 ppm. This is an important test in Aquaculture systems, but is not seen as often in aquaponics. The recirculating nature of aquaponics tends to remove Carbon Dioxide before it gets to high. Levels in my system run 0-20ppm. It is recommended that levels remain below 20ppm, although some data indicates that fish can be acclimated to levels much higher. This is another test that is not required.
LaMotte Salinity Test Kit Model POL-H Code 7459-01
Retail Price: $58.40
For measuring both low and high salinity levels in ponds, recirculating systems, brackish waters, etc. Testing takes 5 minutes. 0 to 20 ppt (parts per thousand) in .4 increments. This is a simple titration test. This test is only useful in systems medicated with salt, as otherwise salt is toxic to plants. There are also less expensive test that are less accurate but adequate.
Lamotte Manganese Test Low Range Model LMN Code 3588-01
Retail Price: $94.99
Manganese is one of the most common metals present in nature and is used in many industrial applications, for example, in the production of fertilizers and in the pharmaceutical industry. It is an important trace element required by plants. This test takes about 3 min. to complete and is read by placing the treated test sample in a color comparator.
This is another test that is generally not needed in hobby aquaponics.
API Freshwater Master Test Kit
Retail Price: $19.99
Fast, easy to use, and accurate liquid test kits. Comes complete with with test tubes, test tube holders, snap tight caps and complete instructions. Includes information on what test results mean and how to correct any unsafe water conditions. Includes tests for pH (6.0-7.6), high-range pH (7.4 - 8.8), ammonia, nitrite and nitrate.
This is the a must have for every aquaponic system. It easily and inexpensively tests the key parameters we care about, especially when cycling a system.
Many of these kits are available from http://www.aquaticeco.com. Another good low cost source I have found is Larkson Lab and Supply. http://www.clarksonlab.com/vLam.pdf
There are many many choices in test kits. Generally they are not needed and performing a quarterly water quality test with a reputable lab can be more cost effective and accurate. There is some value in knowing week to week what certain key levels are.
In my experience after a system has stabilized (6 months), then there is little change in key levels and only a few elements need supplemented on a regular bases (iron, potassium, magnesium in my system). Assuming your system is not overloaded on the fish component, then the plants themselves will tell you what is missing.