Water changes can look very different within different hatchery setups.
If you’re working in a lab setting with a system that has the same water going through constant filtration (such as a recirculating aquaculture system) or are using a system where water is being constantly replenished (such as a flow-through system), water changes won’t be necessary. The filtration and/or replenishing of seawater acts as your water change, removing contaminants from the tanks. Because of the constant flow of water, there is a very short timeframe in which contaminants are able to thrive within the tank—therefore, little time to harm your kelp seed.
Flowthrough nursery system with trickle of water into the tank.
However, if your hatchery has a closed culture system where water is not being constantly filtered or replenished (as is most common for small and non lab-based hatcheries), you should change 100% of the water in your tanks once per week. You may be able to wait ten days to two weeks without a water change, but you’ll increase the risk of contamination and poor water quality.
Keeping in mind that everyone’s process for water changes will look a little different, here are a few strategies you can follow:
Leave the spools in their tank
Leave the spools in their tank. In this option, you will drain the old water from your tanks through either a drain hole plumbed into your tank or a siphon. After you’ve drained all the water from the tank, immediately refill with chilled, filtered seawater. The downside to this strategy is that you will not have the chance to bleach or clean the walls of your tanks and plumbing. This runs the risk of allowing any contamination that was stuck to your tanks and pipes to continue to proliferate.
Bring your spools to a temporary holding tank
In this method, you remove your spools from their tank and place them in a separate holding tank filled with chilled, filtered seawater. Then, you drain and clean your dirty tanks. Once the tanks are clean, fill with chilled, filtered seawater, and place the spools back in place. The downside of this method is that if you are storing spools from multiple tanks in the same holding tank, contamination will likely spread.
Transfer spools to their own new tank with chilled, filtered seawater
This requires double the amount of equipment needed for your setup and is the most tedious option, but it allows you to thoroughly clean old tanks and eliminates the risk of spreading contaminants to other tanks. Once per week, you remove your spools from their tanks and transfer them to an identical setup. Then, you empty and thoroughly clean the old tanks. A week later, once the tanks are clean and refilled with chilled seawater, the spools can be transferred back.
Hatchery technicians performing a water change on the bottom row and placing spools in the freshly prepped tanks above.
Industry Tip
Be sure to have chilled, filtered seawater prepared the night before a water change!
