Aquaponic Cultivation Tips

In preparation for recent workshops, I compiled a list of cultivation tips. Some of these are no-brainers, while others may be less obvious to the Aquaponic newbie. Keep these guidelines in mind as you set up your new Aquaponic system, and your fish and plants will thank you.

    General Tips

• Invest in a pH kit and test the pH of the water periodically. 

• Plants generally prefer pH slightly acidic water (6.5-7pH and fish generally prefer slightly alkaline water (7-7.5pH). Many Aquaponic gardeners shoot for a 6.8-7.0pH range. 

• Your water must stay within 6.0-8.0pH range to allow the process of nitrification. Otherwise your plants won’t grow well, and your fish may suffer, too. Sudden changes in pH can harm your fish, so make changes to water pH slowly.

• It’s a good idea to invest in an ammonia, nitrite and nitrate test kit as well. You can buy a kit that will test pH, ammonia, nitrite and nitrate, for about $25.

         Tips for Fish

• Rinse your gravel thoroughly. Dirt will clog gills and harm your fish! 

•  If you know someone with an aquarium, “seed” your new sponge filter by squeezing their established filter bacteria over your new sponge. This will speed up the time it takes to cycle your fish tank.

• Always use non-chlorinated water. If you have municipal tap water, then pour two 5 gallon buckets (for a 10 gallon fish tank) and leave them outside. The chlorine gas will escape and the water should be safe to use after a couple of days. You can also treat water with de-chlorinator additive, found at a local pet store. 

• Collect rainwater in barrels to re-use the water in your fish tank – the plants prefer water that’s slightly acidic anyway, and there is no chlorine to worry about.

• If you see your fish with red gills, swimming erratically, then you may likely have an ammonia problem. Remember, “Dilution is the Pollution Solution”. A quick water change can help if you notice the problem in time.

• After you set up your fish tank, remember to do partial water changes (about 20-25% of your water) every few days for the first couple of weeks. Don’t change more than ½ of your water at one time. 

• If you are not over-feeding your fish, you should be able to reduce water changes to once a week or so after that. If the solids are accumulating on the bottom of your tank, remove them with a siphon.

•  Don’t over-feed your fish! Feed them what they can consume in 5 minutes or less. If a fish dies, then don’t feed any surviving fish for a day or two. It’s better to under-feed than over-feed.

• Regularly inspect your fish for changes in behavior. You may be able to double or triple the time between water changes in the tank if you start out slowly and don't over-stock your fish tank.

•  Stock your tank no more than 1" for every gallon of water, at the size your species of fish will grow to maturity.

• Stocking density "Rule of Thumb" is 1 pound of fish for every 5-10 gallons of water.
  

• If you have the space, most Aquaculturalists will tell you that a round fish tank is best. But, plenty of Aquaponic gardeners grow in rectangular and square tanks that do just fine.
  

• In general, bigger fish tanks tend to be more stable, and it is best to shoot for at least 90- 100 gallons if you are growing edible fish to plate size.

         Tips for Plants 

• When starting your system, at first consider plants that require low-nutrient levels as it can take a while to fully “cycle” your water and get your fertilizer levels (nitrates) up!

• It’s OK to transplant small starter plants, just be sure to remove all the dirt from the roots! 

• If you are using low wattage fluorescent lights, the closer the better - keep them about 1-2” above the plants. Remember that lighting intensity is cut in half when distance from plant to light is doubled.

• Make the sides of your glass fish tank opaque to prevent algae growth, which will kill the roots of your plants. Simply covering three sides with a black garbage bag will work, and still allow viewing access to the fish, but it will warm up the water temperature. 

• For maximum natural sunlight exposure, South facing windows are best. But be careful to watch the temperature fluctuations, as big spikes can harm both plants and fish.  

• If you harvest all of whatever you’re growing and re-plant new, the baby plant roots won't be able to absorb as many nutrients as your mature plants. Keep water changes in mind when you replant.

• If you use sea salt to cure sick fish, your plants won’t like it.

• For media filled growbed systems, you will want to have at least a 1:1 ratio of 12" deep grow bed volume to fish tank volume.  Much less than this will not provide adequate filtration for your fish.  You can go all the way to a 3:1 grow bed to fish tank volume, but remember there is a limited amount of nutrients available in the water for the plants, your plant growth will likely suffer beyond 3:1.