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So what effects the difference in speed of maturity between fish???

Magnum Man

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It seems there is a big difference in how fast some fish grow… of the fish varieties I currently have, the Cory’s, and Panda Garra’s are 2 of the fastest growing ( of course the Tilapia, that I raise for food ) all seem to grow very fast… whereas angels, Tin Foils, Denison Barbs, and rainbows all seem to grow much slower… then there is also a lot of difference in how fast some fish color up, or mature I have some African Tetras, and rainbows, that are taking years to mature… are the slower maturing fish, longer lived, and the faster maturing fish shorter lived, or is there something else going on here???
 
Genetics, evolution.
Tilapia are food fish because their growth can be so rapid. It's why they're also extinction machines when introduced into habitats with slower growing fish.

An interesting thing is found with wild swordtails. Males mature in 2 waves. The first ones are fast, showy and short lived. Some of their brothers from the same drop will mature slowly, give rise to too many stories about females turning male, develop less showy swords and more robust bodies, and live long lives.

In the killie world, there are Savannah species that are sexually mature adults in a few weeks, and dead in a few months, in one season. In more stable rainforest enviroments, related fish mature much more slowly, but if they don't get picked off by predators, can live and breed for many more seasons. The short lived ones produce lots of eggs very fast, while the long lived ones produce small numbers daily when the food is good.

The quick growing ones (Nothobranchius) are becoming important in aging research, as even in ideal aquarium conditions, their bodies collapse at the same speed they do in a drying up Savannah pool. A short life is in their genes.

I've noticed that cardinal tetras grow to the seasons. They aren't fast, but they breed around December, and they grow to be ready when the rains come to Amazonia. The little ones I bred were the same size as small ones I bought recently, and they'll all make breeder size right around November. So they can be seasonal growers.

Generally, I've found that the quicker the growth and maturity, the shorter the life.
 
of course there are some critters we can speed up, with increased temperatures, and I thought maybe the cooler temps might slow things down, but the Pandas are in a tank with temps in the low 70's ( as are the Denison's & the Tin Foils ) yet the Pandas leapt, from a 1/2 inch to 3 inches, in a few months, yet the immature Denison's maybe grew, a 1/2 inch in that same time frame, and in the same tank... so, would one expect the Pandas to be a shorter lived fish, than the Denisons???
 
To know why a fish grows as it does, assuming it isn't overcrowded, is properly fed and has clean water, you need to do a deep dive into its natural history. What does it eat, what eats it, what are seasonal changes, how deep in the water it favours, etc. It gets really complex.

I know nothing of panda garras. I don't have Asian fish, just because. I think they're cleaner fish. Maybe they need to get big enough to be recognized so they don't get eaten when they approach 'clients'? That's speculation though. There have to be reasons why quick or slow growth give advantages.

I always thought that Nothobranchius killies' quick growth was entirely due to their unstable environment and their water drying up as the rainy season stops. Then I learned that in some habitats, they hatch ahead of the bugs. And the water bugs, which get large, eat them soon around when the Notho eggs are produced. It's a deadly race. By the time the water is drying up, there are no fish.

Man, that gets complicated. Once we have to look at insect life and variables like that, whoah. We are going to have questions that are hard to answer. I love trying.

Nothos are just one example, but there are lots of fish to figure out. Chances are, someone else has tried and maybe done it, but finding what they've shared is hard. If we could each have a couple of selves, and put one to work on research while the others go to work, take care of the kids etc, we could do it.
 
it's getting harder & harder to pull myself away from my comfortable seat, in front of my tanks, and go to work, in the morning... at least I can see the light at the end of the tunnel, as far as my "work" goes... I need to quit going to town all day, so I can do more around the farm, & my tanks
 
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Lots of people say rainbowfish from Australia and New Guinea grow slowly but that isn't my experience. Under good conditions I have had rainbowfish like Melanotaenia trifasciata, lacustris, herbertaxelrodi and others reach 2-3 inches in 2 months from hatching. I have had them reach 4 inches in 6 months in aquariums and 4 months in ponds.

With rainbowfish it comes down to food and water volume. My rearing tanks were 2 foot long x 10 inches wide x 12 inches high. The temperature was 28C. The tank had a thin layer of gravel and an air operated sponge filter. I fed the fish 3-5 times a day and gave them as much as they could eat. I did a 50-75% water change and gravel cleaned the substrate every day. The fry would reach 2-3 inches in 2-3 months in these tanks.

When I put the same fry in 10 foot diameter ponds that were 30 inches deep, I could get them to 4 inches in 4 months and 5 inches in 6 months. If they were in the ponds for 6 months they got deep (high) in the body and were quite large when removed. This happened when I fed the fry lots of food in the ponds. If I didn't feed them much in the ponds, they grew slower and took 3-4 months to reach 2-3 inches and about 8-12 months to get to 5 inches.

More food means faster growth.
Larger water volumes equals faster growth.
Warmer water means faster growth (28C being the optimum temperature for growing most tropical fishes).

Some fish naturally grow faster than other fish. In nature most fish that grow to less than 12 inches long will be sexually mature within 6-12 months of hatching, and most will be close to full size in that time. Fish that grow bigger than 12 inches usually take 2 or more years to become sexually mature and all fish continue to grow throughout their lives, albeit at a much reduced pace when they have hit close to maximum size.
 
One of the early lesson I learned in this hobby was about fish lifespans and that in tanks many fish will generally live longer on average than they do in the wild. There are several reasons that this is the case.

1. They do not have to deal with predation.
2. They eat more regularly.
3. They may eat better food in terms of nutrition.
4. We try to cure sick fish and often succeed whereas they would be more likely to die in the wild.
5. They do not have to deal with natural phenomena like drought, famine or humans degrading their habitat.

And it would seem logical that the slower a fish grows, the longer it might live. A fish which need 5 years to reach adulthood has to live a longer life than one which becomes an adult in 18 months. That is not rocket science though.

edited to fix typos
 
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