- A media bed performs three filtering functions;
- mechanical (solids removal)
- mineralization (solids breakdown and return to the water)
- bio-filtration
- The industry standard is to be at least 12” (30 cm) deep to allow for growing the widest variety of plants and to providec omplete filtration.
- Must be made of food safe materials and should not alter the pHof your system (again, beware of concrete).
- If you have flexibility here, 250 gallon (1000 liters) orlarger seems to create the most stable aquaponics system.
- Must be made of food safe materials and should not alter the pHof your system (beware of concrete, for example).
- 1 pound of fish per 5 – 7 gallons of tank water (.5 kg per20-26 liters)
- Determine the total grow bed area in sq ft (or sq m)
- From grow bed area, determine the fish weight required (poundsor kg) using the ratio rule 1 lb (.5 kg) of fish for every 1 sq ft(.1 sq m)of grow bed surface area, assuming the beds are at least12” (30 cm) deep.
- Determine fish tank volume from the stocking density rule above(1 pound fish per 5 – 7 gallons of fish tank volume or .5 kg per20-26 liters). When your fish are young and small, reduce thenumber of plants in proportion to the size of the fish and theircorresponding feed rate / waste production.
- Hydroton), LavaRock, and Gravel are the most widely used media types. If youchoose gravel, understand it’s source and avoid limestone andmarble as they could affect your pH.
- You should flood, then drain your grow beds. The draining action pulls oxygen through the grow beds. The least complicated way to achieve a reliable flood drain system is using a timer.While more complex, siphons are also excellent options foraquaponics.
- If you are operating your system with a timer you should run it for 15 minutes on, and 45 minutes off.
- You want to flow the entire volume of your fish tank through your grow beds every hour if possible. Therefore, if you are running your pump for 15 minutes every hour (see above), and you have a 100 gallon tank, you need at least a 400 gallon per hour(gph) pump. Now consider the “lift” or how far againstgravity you need to move that water and use the sliding scale thatis on the pump packaging to see how much more power you need beyond the 400 gph.
Ammonia, Nitrites, Nitrates – after cycling,
- Ammonia and Nitrite levels should be less than .75 ppm
- If you see Ammonia levels rise suddenly, you may have a deadfish in your tank.
- If you see Nitrite levels rise you may have damaged thebacteria environment in your system.
- If either of the above circumstances occur, stop feeding yourfish until the levels stabilize, and, in extreme cases, do a 1/3water exchange to dilute the existing solution.
- Nitrates can rise as high as 150 ppm without causing a problem,but much above that, you should consider adding another grow bed toyour system.
When to add plants
- As soon as you start cycling your system, but accept that theymay not grow well for the few weeks required for cycling tooccur.
- If you add Maxicrop Liquid Seaweed to your tank when planting(Australians call this Seasol) at the rate of 1 quart bottle per250 gallons (1000 liters), your plants will establish themselvesmuch more quickly.
- You can place your plants roughly twice as closely together asyou would in soil.
Feeding Rate
- As much as your fish will eat in 5 minutes, 1 – 3 times perday. An adult fish will eat approximately 1% of itsbodyweight per day. Fish fry (babies) will eat as much as7%. Be careful not to over feed your fish.
- If your fish aren’t eating they are probably stressed, outsideof their optimal temperature range, or they don’t have enoughoxygen.
PH
- Target a pH of 7.0, in your aquaponic system. This is a compromise between the optimal ranges of the fish, theplants, and the bacteria.
- Test pH at least weekly, and as frequently as 3 – 4 times perweek.
- During cycling pH will tend to rise.
- After cycling your systems, pH will probably drop below 7.0 ona regular basis and require being buffered up. If you need tolower pH it is generally because of the water source (such as hardground water) or because you have a base buffer in your system (eggshells, oyster shell, shell grit, incorrect media).
- Best method for raising (buffering) pH if it drops below6.6
- Calcium hydroxide – “hydrated lime” or “builder’s lime”.
- Potassium carbonate (or bicarbonate) or potassium hydroxide(“pearlash” or “potash”).
- If possible, alternate between these two each time your systemneeds the pH raised. These also add calcium and potassium,which your plants will appreciate.
- While they work, be cautious about using natural CalciumCarbonate products (egg shells, snail shells, sea shells). Theydon’t do any harm, but they take a long time to dissolve and affectthe pH. So, you add it, check pH two hours later and nothing haschanged, so you add more. Then suddenly, the pH spikes because youhave added so much.
- Best methods for lowering pH, in order of preference, if itgoes above 7.6
- pH Down for Hydroponics- (be careful of using the aquariumversion as this has sodium that is unhealthy for plants).
- Other hydroponic acids like nitric or phosphoric as theplants can use the nitrate or phosphate produced.
- Other acids, such as vinegar (weak), hydrochloric (strong), andsulphuric (strong) – last resort as directly adding these acids toyour system could be stressful for your fish.
- Use caution when adding anything to your system containingsodium as it could build-up over time and cause harm to yourplants.
- Do not use citric acid as this is anti-bacterial and will killthe bacteria in your bio-filter.
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