what temp for flowerhorn?

[RD.]

RD I've been curious...is there a study that shows a 'curve' of increased bacterial disease issues vs temps? I too have read conflicting information on FH temps from 'experts' who claim since they're raised in warmer water at the farms its okay.

Yes, numerous papers/studies on this subject, including columnaris aka duck lips, a common disease among FH.

Just one example…..

Columnaris disease in fish: a review with emphasis on bacterium-host interactions - Veterinary Research

Flavobacterium columnare (F. columnare) is the causative agent of columnaris disease. This bacterium affects both cultured and wild freshwater fish including many susceptible commercially important fish species. F. columnare infections may result in skin lesions, fin erosion and gill necrosis...

veterinaryresearch.biomedcentral.com

4. Importance of environmental factors
Karvonen et al. described the effect of global warming on the prevalence of different fish parasites and bacteria [104]. F. columnare could be one of the many taking advantage of this phenomenon. Indeed, transmission of columnaris disease is more efficient in higher temperatures [30, 105]. Holt et al. found that when steelhead trout (Salmo gairdneri) or coho salmon (0. kisutch) experimentally infected with F. columnare were held in water at 12 to 20°C, mortality increased with temperature [106]. As stated above, adhesion to gill tissue of a highly virulent F. columnare strain is enhanced at increased temperature [61] and chondroitin AC lyase activity of this pathogen increases along with the temperature [107]. The influence of rearing density and water temperature in rainbow trout was studied by Suomalaien et al. [105]. Normal rearing densities with high temperatures (23°C) proved to increase both transmission rate of columnaris disease and mortality in the fish.

 

[RD.]

More fun reading .....

Temperature-dependent expression of virulence genes in fish-pathogenic bacteria - PMC

Virulence gene expression in pathogenic bacteria is modulated by environmental parameters. A key factor in this expression is temperature. Its effect on virulence gene expression in bacteria infecting warm-blooded hosts is well documented. ...

www.ncbi.nlm.nih.gov

 

[DN328]

Don't believe everything that you read. FH's are a hybrid cross of CA cichlids, species of fish that did not originate in year round temps of 84F. In a closed system such as an aquarium, bacteria thrives at these higher temps, making a perfect breeding ground for disease such as Flexibacter columnaris, more recently named Flavobacterium columnare aka duck lips. Exactly why one sees so many FH topics with "duck lips".

I suspect that some of the early breeders of FH felt that higher temps were better, as most of the designer fish have delicate immune systems, and higher temps gives the entire metabolism a boost. That, and at higher temps with a higher metabolism one can power feed more which results in increased growth in juvenile fish, which allows breeders to get their fish to market fa$ter. Good for the breeder, but overall maybe not so good for the longevity of the fish.

I've grown out several FH over the years, all imported from Bangkok, and they all did just fine at 78-79F.

Thanks for sharing this, and it makes a lot of sense. In the past when I see signs of ich, I would increase my regular set temp ~79F, slowly up to ~89F for about 10-12 days. This seems to resolve the ich issue without any salts or meds. Based on the points you made, one shouldn't keep the temperature high for too long beyond the period t address the ich, else you're creating additional issues. Is this rationale correct or am I missing something (time factor?).

 

[RD.]

All bacteria have ranges in conditions for optimum growth, temperature, pH, hardness, etc, and certain conditions also allow for better adhesion to gills, such as hard water, and columnaris bacteria. Excessive crowding, higher organic levels, aggression from tank mates, breeding, etc, all add to the stress level in the tank as well. Temperature of the water is just one parameter to be mindful of, and from everything that I have read over the years higher temps invite a higher risk of ones fish succumbing to some of these pathogenic bacteria. The first thing that most people will advise when columnaris surfaces, is to turn your heaters down and keep the water in the low to mid 70's. That single act will help keep the bacteria in check while one works on treating the fish, or at the least correcting some of the conditions that have caused the outbreak.