I'm day 6 in, trying to kill what I think is GHA, and as far as I can tell there is little change, although I sometimes see the odd bit of algae floating around in the water. When would I know if I need to second dose, and how do I do that?
If you removed the activated carbon filter, skimmer cup (keeping the skimmer turned on for oxygenation) and turned off the UV filter, the effects of fluconazole tend to persist for a long time in the aquarium due to its molecular stability and there are control reports of GHA in 03 weeks or more with a single dose, but ... it is very necessary to keep an eye on the parameters, since the death of the algae returns many nutrients to the aquarium and, if they are toxic algae, they can have unwanted side effects .
If, during the course of the treatment, undesirable side effects or significant changes of any parameters are observed, partial water exchanges may be made by maintaining the same proportion of medicament from the first dosage in the exchange water.
GHA and BHA are often much more resistant than Bryopsis to the effects of fluconazole and some strains may not respond to treatment, but if signs of drug action are observed, such as developmental stopping, bleaching of the tips or changes in color of the structures algae, it is to be expected that its control is a matter of time and in such cases the best course is to perform partial water exchanges when necessary, replacing fluconazole in the exchanged water to maintain the initial concentration, until you get the control.
PS: Still, and as an aquarist, I must say that fluconazole gives us the opportunity to control an outbreak of difficult algae, such as Bryopsis, which for many years was considered a terrible plague and often because it is so resilient to control , came to determine the dismantling of many aquariums and discourage many other aquarists from continuing in the hobby, but giving us the "opportunity" should not be considered as having given us the "solution" ... the real solution is to persist in the pursuit of balance of parameters and persist in careful observation of everything that happens and everything we put in our aquariums, especially quarantining all animals and carefully inspecting all coral bases and shells of molluscs and gastropods, to avoid as much as as is possible, the undesired introduction of these pests.
In doing so, we certainly will not find it so necessary to resort to medication.
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