One of the facts of many aquaculture facilities is that your fish are going to need to be treated for gill and external parasites or fungus. Be it chloramine T, Parasite S or Peroxaid, the frequency of treatments depends on many factors specific to each facility.
August 23, 2018 By Ron Hill
Treatments are one of the aspects of fish culture that farmers like the least, but is a necessary expense. Employees are generally reluctant to deliver treatment to tanks as many of the chemicals are unpleasant to handle and the risk to the fish while the treatment is active is considerable. Any errors in concentration can result in fish losses or ineffective treatment.
Proper deployment and timing of treatments can make a big difference on how often you treat overall. Properly managing how and when you treat can lead to savings in treatment products but also makes your staff more available and your fish healthier.
When to treat
When to treat is one of the toughest things to get across to new workers. Experienced farmers will know the difficulties. The most obvious answer to the question is, “when the morts are on the rise over several days. When I see the fish need treatment because a portion of the population is being affected or distressed.” However, this is not the right time to treat. When you get to this point, you may have already missed the right time to treat. You are still going to treat them right away but you are already into damage control. You are now looking at a three-day treatment with fish losses during and after the treatment as the moribund ones die off. Effective use of treatment at this point is certainly the right move and saves your fish from an outbreak.
An experienced farmer, however, knows treatments are best used as a preventative measure or prophylactic. It is always better to treat early than to treat often. If this pattern repeats in other tanks around your system how many fish will it cost you in total?
Treat before it’s needed
Instead of treating when you see the fish are starting to be affected, you need to treat as soon as the first signs appear on your fish and in your morts. When you see the odd fish showing possible symptoms, that is the time to treat. “You need to treat them before they need to be treated,” is how one old farmer described it to a new worker. If you treat early enough you should be able to knock back the infection or parasite with minimal product used and minimal fish lost.
Historical data is critical as well when deciding to treat. Knowledge of what pathogens occur in the water, what life stages are usually affected, the usual symptoms and visual cues that predict an outbreak is also important. Workers on the ground must be trained to recognize these symptoms as soon as they appear and suggest treatment. The people who are on the ground, who feed and pick morts each day are the ones that see each tank each day. Relying on supervisors to observe and decide on treatment can be effective, until things get busy.
Some hatcheries circumvent issues with a treatment schedule. A schedule can be an excellent tool for disease prevention if it is managed properly. With knowledge of the facility history and operations, treatments can be scheduled before predicted outbreaks or at prescribed intervals. Because there is a schedule, employees tend to follow it and don’t think outside the schedule.
If you have a facility with persistent problems, consider post-handling treatments. After any event where the fish are handled they should be scheduled for treatment. Outside of usual preventative treatments or scheduling, fish that have been handled or stressed should get treated after grading, moving/splitting, vaccinating and fish entry. When the slime coat and scales have been affected by handling, the fish is vulnerable to background pathogens in the system. The benefits of the treatment will outweigh the stress except in extreme cases.
Bang for your buck
Properly choosing when to treat is the best step to get the most of your treatment dollar but there are some other ways to ensure you are getting the most out of each treatment.
Lower the tank level. When performing a bath or flow through treatment, drop the level in the tank as low as you are comfortable with – usually around half. Half the volume, half the treatment used.
It’s amazing what salt can do. Simple un-iodized salt is a versatile and cost-effective treatment product that can be used in many ways. It can greatly increase the effectiveness of other treatment products. Salt is an effective pre-treatment for fish with gill issues and is often used in conjunction with Peroxaid or Chloramine T. The addition of background salt to your RAS system is a great preventative measure to fight background pathogens and fungus.
Check the concentration. It’s easy to use the prescribed buckets with lines to measure treatment products but once in a while recheck the level of concentration that you are treating at and test the tank during the treatment to see what it is. Make sure you are getting good mixing when you add the product so the concentration is uniform.
Eliminate flow-through treatments. Unless you feel you need the incoming water, switch to a bath style treatment with no or very little incoming water. Some facilities won’t have enough faith in their stand pipes to turn the water entirely off. Bath style treatments save a large amount of treatment product overall and give better quality contact time.
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