Have you actually witnessed it or just another unsubstantiated claim.
JD has the same size as GT. Their average life span is 10 years and once reaching max size of 10 inch in 4-5 years, they stop growing, age and develop crooked back.
jack dempsey growth and max size?
- Thread starter jagsandpits
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JD has the same size as GT. Their average life span is 10 years and once reaching max size of 10 inch in 4-5 years, they stop growing, age and develop crooked back.
I have seen quite a few in the 10" and slightly larger sizes, some in large tanks, some in nature, and without the unnatural arched backs. There was a large pair at the Shedd Aquarium in Chicago some years back in a 300ish gallon tank, where the male easily hit 12" and was magnificent in color and form.
I believe the small sizes, and arched backs have to do with the bad water quality that occurs in most tanks that are in reality, way too small, and where water changes are too few, and far between.
In the Cenote's where they live in the Yucatan, there is a constant upwelling of new water from below, giving them a constant 100% water change, and where nitrate levels in the Cenotes are near zero. And many alpha pairs stake out territories directly in the flow of the up-wellings.
A 50% water change of once per week in an aquarium is paltry in comparison, so slow growth, and chronic problems are often the result, especially in tiny tanks of less than 100 gallons.
I believe the small sizes, and arched backs have to do with the bad water quality that occurs in most tanks that are in reality, way too small, and where water changes are too few, and far between.
In the Cenote's where they live in the Yucatan, there is a constant upwelling of new water from below, giving them a constant 100% water change, and where nitrate levels in the Cenotes are near zero. And many alpha pairs stake out territories directly in the flow of the up-wellings.
A 50% water change of once per week in an aquarium is paltry in comparison, so slow growth, and chronic problems are often the result, especially in tiny tanks of less than 100 gallons.
I have been to Shedd Aquarium and it's the best freshwater fish collection public aquarium. I saw 20+ inch oscar and Dovii there that I have never seen before, but don't recall seeing any super size JD or GT exceeding 12".
For large cihlid such as Oscar and Dovii, captive grown fish rarely reach maximum potential due to tank size constrain. Smaller cichlid, on the contrary, often reach immense size not seen in the wild due to unconstrained tank size and nutrition. Mubuna and Aulonocara species, for example, often reach size double their wild cousins. JD and GT are mid size cichlid, and I don't think tank size constrain their maximum size potential.
Larger cichlid also live longer than smaller cichlid. For example, Rams live for about 3 year, JD and GT 10 year, and Oscar and Dovii 15 year and beyond. Since it takes longer time for large cichlid to stop growing, the probability of losing them before reaching max potential is high.
I don't doubt that Duanes has seen 12" JD, but having visited many public aquariums in US and oversea, I haven't seen one that large. IME raising JD and GT, they grow rapidly in the first 3 years to nearly max size, stop breeding in 5 , and go into aging decline after 7 and stop growing. In contrast, my larger Vieja species continue to grow slowly and eat with good appetite at 7 with no sign of aging, so I expect them to reach 15" and beyond.
For large cihlid such as Oscar and Dovii, captive grown fish rarely reach maximum potential due to tank size constrain. Smaller cichlid, on the contrary, often reach immense size not seen in the wild due to unconstrained tank size and nutrition. Mubuna and Aulonocara species, for example, often reach size double their wild cousins. JD and GT are mid size cichlid, and I don't think tank size constrain their maximum size potential.
Larger cichlid also live longer than smaller cichlid. For example, Rams live for about 3 year, JD and GT 10 year, and Oscar and Dovii 15 year and beyond. Since it takes longer time for large cichlid to stop growing, the probability of losing them before reaching max potential is high.
I don't doubt that Duanes has seen 12" JD, but having visited many public aquariums in US and oversea, I haven't seen one that large. IME raising JD and GT, they grow rapidly in the first 3 years to nearly max size, stop breeding in 5 , and go into aging decline after 7 and stop growing. In contrast, my larger Vieja species continue to grow slowly and eat with good appetite at 7 with no sign of aging, so I expect them to reach 15" and beyond.
The largest ones I've seen were not near the surface areas but held territories at depths below 10', I saw one large male guarding the entrance to a large cave, that's easily over 10".
That said....some years I only saw small to medium sized individuals, as if its a cyclical thing.
One year there were 7"-9" mollies, the next year they were gone and the only ones I saw, were 3-4".
But much of this had to do with the day of the week, on weekends when local kids used the Cenotes as swimming holes, constantly diving off cliffs, the large fish of all kinds hid out.
I also don't believe JDs are the exception to other cichlids that grow throughout their life spans. If conditions are right, although some slowing down at a certain point would be normal.
I believe most stop growing in tanks because water quality in the form of nitrate, is acutely problematic, and effects growth.
For medium to large cichlids that come from pristine waters with practically 0 nitrate, the accepted aquarium norm of 10 -20ppm is a large contributor that slows normal growth, and overall health.
That said....some years I only saw small to medium sized individuals, as if its a cyclical thing.
One year there were 7"-9" mollies, the next year they were gone and the only ones I saw, were 3-4".
But much of this had to do with the day of the week, on weekends when local kids used the Cenotes as swimming holes, constantly diving off cliffs, the large fish of all kinds hid out.
I also don't believe JDs are the exception to other cichlids that grow throughout their life spans. If conditions are right, although some slowing down at a certain point would be normal.
I believe most stop growing in tanks because water quality in the form of nitrate, is acutely problematic, and effects growth.
For medium to large cichlids that come from pristine waters with practically 0 nitrate, the accepted aquarium norm of 10 -20ppm is a large contributor that slows normal growth, and overall health.
