Tank Temperature And Fry Growth

[BitterCowgal]

I've been doing a LOT of reading since my fry were born. So far I've found several websites stating that a temperature of 78 to 80 degrees F is beneficial for fry growth.

The basic jist of it is that higher temperatures = higher metabolisms in the fry. Higher metabolisms = eating more...eating more = faster growth. So far this seems to be holding very true for my fry.

I have all but three of my fry in my main tank. I maintain a temperature of 78 to 80 degrees in my main tank at all times. These fry are quite large at the moment compared to the three fry in the Nursery tank. The Nursery tank has a temperature of 75 degrees F at all times.

The fry in the 78 - 80 degree F tank are approx. 1/2 inch in length. Perhaps a bit larger even. Colors are coming in quickly and are bright and vivid.
The fry in the 75 degree F tank are only about 7 or 8 millimeters in length. Colors are very slowly coming in.

The fry in both tanks are the same age, 13 days old at the time of this writing. The fry in my main tank (the warmer tank) are being fed crushed New Life Spectrum Community pellets...the fry in the Nursery tank are being fed Hikari First Bites. Not sure that diet would affect growth so much though as for awhile both tanks of babies were eating the Hikari.

Has anyone else observed that higher temps = faster growth?

 

[Spader]

higher temps = more males ive read. i want more females so i keep it 76-78.

 

[BitterCowgal]

higher temps = more males ive read. i want more females so i keep it 76-78.

I've read that too in a few places but I've also read that PH is also a factor influencing gender. This threads not really about gender though. I guess it is now.

New question then...

If hypothetically High Temp = Faster growth and High Temp also = more males...what happens when you add High PH into the mix? High PH should theoretically = more females.

In summary the theory goes as follows...
High Temp = Fast Growth
Low Temp = Slow Growth

High Temp = More Males
Low Temp = More Females

High PH = More Females
Low PH = More Males

However...nearly all of the sources I've read state that the observations on the influence of Temp and PH on Fry Gender tends to vary from species to species. With some species, neither variable appears to have an effect the final outcome of the genders of the fry. I raise swordtails only at the moment. I have yet to find viable information regarding the effects of temp and PH on swordtail fry specifically. So...these two theories have yet to be proven.

All sources regarding the theory of higher heat yielding faster growth have been consistant regardless of species. For growth it's a matter of metabolism and since higher temperatures increase metabolism it stands to reason the fry would grow faster.

It'll be rather interesting to see how my High Temp/High PH tank pans out as far as fry gender ratios.

 

[Rafael Dilone]

Well in my tank were I have my fry (until they are move to the fry tank) the temperature is between 80-82 F. There growth is very quick. Most 1/2 inch and they are 2 weeks old and some 4 weeks old. Before when I had other fry they had a temperature of 72 F and it took them much longer to grow. It took one of my guppies 8 months for it to reach adult size from the day it was born. I have also heard after the fry are old enough to mate ( 3 months or so) if they are kept from having sex they will grow to be almost twice as large. It is just a rumors I heard.