Fry Growth Rates When Removed From Parents

[Melody]

I've heard both versions for various fish - some say they grow quicker with the parents, others say they grow slower.

I've never really noticed to tell you the truth, I just do what I have to do to best utilize my tank space.

However, today I noticed that the few fry I netted from the adult tank with Limia Perugia are noticeably larger than the fry left in the tank. Not remarkably, but I noticed it without looking for a difference. I only removed some to ensure that I got my colony established in case something happened in the parents' tank.

Has anyone observed the same thing in other species? I'd like to know one way or another since the observation got my brain to questioning. Maybe it differs depending on the species?

[Edgezilla]

I don't think the parents is a factor in determining the size more so than how much they have to eat 24/7.

If you remove them from the parents, chances are, they have more to eat when they don't have to compete with larger fish or hide most of the time to avoid being devourer.

I have grown one of the largest discus I have kept in a high tech planted tank. What I found was NO3, NO2, NH3, NH4, etc. were not a factor in determining the size of the fish.

[Melody]

I've suspected as much myself. There's supposed to be a hormone involved and I know one is involved in the growth rate in a fry tank, hence the quicker growth with more water changes. I do more changes in the tank they're in, so it may just be that alone too.

[madattiver]

I think there is a huge factor in growth rates that involve temps.. higher temps promote apeptite.. which involves them eating more.. which means more water changes to have better water quality.. which in the end equals faster growth rates.

water quality is huge.. I have notices this by raising several fry in different sized tanks from the same batch.. the ones in the larger tanks that grow faster.. most likely because the water quality doesn't deterioirate as fastly.. even more so a hanging home made breeder basket in a larger tank workes just as well.. greater water volume.. etc.. etc.. and the small confines that they don;'t have to go search out for food.


just a few of my thoughts on the subject.

[Melody]

Yes they all seem to factor in. Growing fry give off a growth hormone into the water, when the concentration in the water is higher, growth slows. Therefore when you're raising fry the frequent water changes remove the hormone so they maintain max growth rates. The bigger the tank, the less concentrated it gets on a regular basis. I think there's more to it than the hormone when it comes to tank size though, because the difference in growth rates can be remarkable. Could be a crowding radar I suppose.

A poluted environment would effect the general health and may bring on low grade infections, etc for them to fight off, taking energy away from their growth.

Heat is an artifical means of speeding growth which should only be used to the max temp recommended for the fish. It speeds the metabolism which initiates the cycle you described, but unfortunately, that will also shorten the lifespan.

Same with too much protein, etc - it works to obtain fast growth, but fast growth isn't necessarily optimum growth. I expect them to grow faster in our care than they would in the wild due to the constant supply of food and lack of energy required to live, but it should still be comparable, not through the ceiling, in my opinion. We want fast growth rates for our convenience, not for the fish.

I also think that vegie eaters should have that in their diet from day one in the form of high protein sources, like algae/seaweed. I have used vegies with fry for a long time, but I hadn't concentrated on high-protein vegies before. I just started doing that now so I can compare the growth rates with protein from 'meat' sources.

I definitly feed my fry tanks more so I think growth rate away from adults would be effected by that. I wonder if there's more to it though....:Think: .

[CACAdmin]

When I scooped my molly fry and put them in the fry tank, I missed one, which I would see periodically but of course was too difficult to catch so I left it in the 70g tank. The day before yesterday, when once again removing fry from the 70g I managed to net the little one who is now in the fry tank with the rest. She is considerably smaller than the rest of the fry in there.

Comparing environments/feeding, etc.
Both tanks: same temperature
Fry tank: more frequent water changes
Fry tank: one additional feeding per day
Fry tank: largest fish - young adult platys
70g: mostly adult fish (including parents), largest are 5 in. gouramis
Fry tank: not always planted (marisa snails frequently devour plants...lol)
70g: heavily planted

Given the above, I can't pinpoint any one factor, so maybe it's a combination. I guess the only way to determine if the extra water changes or the extra feedings are a factor would be if you had 2 identical tanks and upped the changes in one or upped the number of feedings in one. If I had the place to do it (& could afford another 70g :rolleyes: ), it would be an interesting experiment.

[Melody]

Food probably. Increased waterchanges also speed growth rates through the removal of growth hormones. However, they'd be diluted in the 70G so that shouldn't make a huge difference.