When you add new fish to your system, you have to acclimate them to their new environment. Never just dump new fish into a new environment. Sudden differences in the temperature, pH, and hardness between the two environments can shock the fish and kill them. Specific techniques depend drastically on species of fish being introduced and their sensitivity, but we’ll share a general SOP we go by:
Remove 1/2 the water in the current fish bag. Put this bag in the future tank to acclimate the temperature of the bag water. Then remove 1/6 of the water every 10 minutes into the bag as you add the same amount of tank water back into the bag. This acclimation process will take 60 minutes. If the fish is extra hearty, you can shorten the water changes to every 5 minutes and only do a 30 minute acclimation process.
Then, after water quality acclimation is achieved, remove as much of the bag water as possible (to minimize what little original water remaining is still in the bag from transferring) and dump that bad boy in. We don’t recommend using a net to scoop the fish out for many reasons. The biggest reasons for this recommendation is that nets can stress the fish out or even damage their protective slime coat.
All fish will require specific feeding protocols based on their species, current weight, target weight, and other factors like filtration capabilities of the system and total hydroponics grow space. These factors will determine what food you should get (high fat or high protein? fishmeal or vegetarian?) as well as how much you should feed and how often.
Now that your fish are in the system, you’ve officially moved on to the Growth Care stage. This is the longest stage of the aquaculture system lifecycle and depends entirely on the specific fish species you’ve chosen. There are a few overarching considerations that all fish species require.
Similarly, all fish have specific needs for the flow velocity of the system. Some fish like to have strong currents to swim against (like salmon), while other fish like to live in nearly still water (beta fish). Flow rate is determined by your pump size, head height from pump to fish tank, and the diameter of your inlet and outlet pipes in the culture tanks.
Finally, every fish, no matter how healthy, is susceptible to infection, disease, and pests. An important aspect of fish care is isolating any sick fish in a quarantine tank so you can treat them individually without impacting the system at large. A quarantine tank is usually a smaller tank capable of holding a small percentage of your total system capacity. It is an isolated system and usually consists of a fish tank, air pump and airstone, and some sort of filter attachment. The quarantine tank is not used for hydroponic growth because we don’t want to spread fish disease and pests to anything. Once any sick fish are isolated, you can administer any treatments that are usually used to cure that particular affliction. An example would be adding a small amount of mineral salt to the tank to heal up a fish’s damaged slime coat. Slime coats are a protective layer of probiotic microbes that help keep the fish free from disease. These coats can become damaged, making them susceptible to disease. A safe ratio is between 1 tablespoon per gallon to 1 tablespoon per 5 gallons. Don’t add salt to the primary aquaculture units because salt does not evaporate out of the system and will eventually build up to levels that can harm your plants.
Harvesting your fish is an exciting, albeit somewhat miserable experience. The prospect of fresh fish for dinner or a large sale is tempered by poopy fish water splashing all over your face and clothes. High-quality fish harvesting SOPs exist to make your life easier and hopefully just a little less gross. Of course, it is two very different things to harvest three fish from a 29 gallon aquarium versus two hundred fish from a 2500 gallon culture tank. However, no matter your scale, a few key tips can make this process as easy and fast as possible while maintaining safety for the fish at all times.
Harvesting in Cohorts
Unless you are planning to shut down your system, you should never harvest all your fish at the same time. Doing so will remove your ammonia source from the system and will dramatically reduce nitrates as a result, leading to a decline in plant health. The key to avoiding this catastrophe is harvesting up to roughly one quarter of your total fish biomass at once. At the commercial level, the easiest way to ensure this is to keep fish in cohorts, each to their own tank. Each cohort is at a different stage of growth. Typically there are four cohorts, fingerlings (baby fish), juvenile fish, adolescent fish, and adult fish (ready for harvest). After harvesting the oldest cohort, replace them with fingerlings.
Remove all barriers to your net
Make sure the only thing you have to catch in your net is the fish. That means removing any living rock, wood, or plants in an aquarium system and not having to navigate around awkward inlet and outlet plumbing in larger systems.
Lower water level
Fish don’t like nets and they can move on 3 axises to easily avoid your net. Lower the water level in the tank and remove the advantage of the Z-axis. You can use some of that water in the harvest vessel, which will minimize shock as they are harvested. This is most applicable to full harvests of the entire tank. Don’t drain your tank to just get a single fish!
Turn off the air and water flow
Light does funny things when it enters water. Turn off the air and water flow to reduce the turbulence in the tank and you’ll have a way better view when you are netting your harvest.
Have your Harvest Vessel immediately available and ready for receiving
The harvest vessel is whatever container you are putting your harvest into. This could be a small baggy filled with system water if you are just harvesting a few small fish. If you are harvesting commercial fish for processing, the vessel may be a tub of salted ice water, which is used to humanely harvest the fish. If you are harvesting fish for eating, make sure you follow any particular laws in your area. Additionally, some states have regulations for transporting live fish, so check your local laws to ensure you are in compliance if you are transporting fish.
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