Input needed to compare fry growth and water changes

[PseudaSmart, posts: 180]

When the topic of water changes and fry growth is brought up the result is typically a lively discussion. While adding another rack of grow out tanks I started to think about just how much water is needed for maximum fry development and after a point are you just wasting water and time? I realize this is a very complex question and I am not trying to oversimplify it. So using a set of problem solving tools I would like to start looking at different aspects of water changes and fry growth.

The members of this board have a lot of experience and it would benefit the group if some of this experience could be quantified.

The first question in this study is to find out the range of the water changes used in raising fry.
The assumptions for this particular study are:
Food, water quality, temperature, and lighting are adequate.
The growth rate of the fry is assumed to be good
Species has a large impact on growth rate

Here is an example of the information I am requesting
Tank of system name___Total water capacity___% WC___frequency___#fry___species___age of fry
30 gallon tower_______100 gal w/ sump________20%____Daily_______150____L600______3 months
50 gallon tank_________45 gal_________________20%____Daily________75____L160______2 months
(sorry for the underline it was the only way I could get the data to line up)

It would probably be best to PM me the information so it can be tabulated into a common format. Let me know if you want your User Id included on the summary of if you want to remain anonymous. I will share the information as it becomes available (2-3 times a week) and hopefully it will be a launching point for further discussions.

The results should be quite interesting!
Jim

[Shane]

I started to think about just how much water is needed for maximum fry development and after a point are you just wasting water and time?

Jim,
I am not quite sure what you are asking. When you say "how much water" do you mean in terms of tank space available to the fry? Numerous aquaculture studies have shown that the largest factors impacting growth are water quality and crowding. Are you trying to control for one or both of these factors? I realize they are very difficult to seperate when we are talking about an enclosed system like an aquarium. Still, five fry in a ten gallon receiving 20% daily water changes would see much faster growth than a ten gallon tank with 10 fry receiving even more frequent (or larger) water changes.

Regardless of what you are trying to measure, I think it will be a worthwhile effort and contribute to our collective knowledge.
-Shane

[PseudaSmart, posts: 180]

Shane,
You are right at the heart of what I am trying to quantify. There is the assumption that more is always better. At some point in time other factors will limit fry growth such as the metabolic rate of the fry.

Another observation that got me thinking about this topic was a result of an unplanned event. My L600s spawned in a 300 gallon tub. When I collected the fry I was not able to catch them all, not a big surprise considering the number of fry and the size of the tub. For 7 months I did not think any of the fry survived until I saw one one evening. The only other fish in the tank were the parents and some cherry barbs.

This one fry basically had unlimited water and food as compared to the ones I raised in grow out tanks. It was only 15% bigger then the others in the 'cramped tanks'

So you are right, I do not have an exact plan or an expected outcome. I thought it would be interesting to start with seeing the range of water changes and move forward.

Thanks for the interest!
Jim

[Shane]

There is the assumption that more is always better. At some point in time other factors will limit fry growth such as the metabolic rate of the fry.

Yes, and as measured in aquaculture studies these include: stress, O2 levels, temperature, photoperiod, amount of food, and quality of food.

In aquaculture studies they are able to control the "more is always better" factor by using floating pens in rivers. In this manner water quality is kept 100% perfect (or at least 100% natural). What they find however, is that all bunched up in the pen they grow slower due to crowding. It is all a give and take process, but a little hard research should help aquarists balance these factors better.

There are a handful of aquaculture papers done with loricariids for the food industry. My favorite was a huge one done with Loricaria in Venezuela many years ago. Loricaria as an export food fish... really

-Shane

[pleco_breeder, posts: 803]

I haven't kept any data on growth vs. water changes in years. However, I only do 5% daily changes on my pleco systems via sprinkler timer and overflow on the sump. The tanks I currently breed in are 10 gallons with only the adults and any recent fry. Bare bottoms with only a weekly bottom siphoning. All this is done to simulate the dry season. Normally the fry are moved before the first rainy season after hatching. Using this set-up, TDS and BOD increase as the dry season continues with only a slow decrease in ORP. Short of doing a lot more work, it's as stable as it's going to get.

Fry are normally condensed in larger tanks, but those systems are currently down because of a fishroom remodel I've been working on. That has allowed me to remember some of the long forgotten basics. The fry grow as well during the first month as if they were in larger tanks. After that, growth is slower in the smaller tanks even though they still have as much volume per fish. It has been my theory for quite a while that a larger area of substrate (added rock/woodwork) strongly effects growth in Loricariidae. I've never done a study to figure out whether it was caused directly by surface area, more feeding area, territory space, decreased aggression due to more hiding places, or some combination of all. However, it becomes obvious after a couple months even when comparing from the same spawn in two different tanks on the same central system.

Even now, I have two groups of L184 from the same source with 4 fish in each group. These were bought to grow out as future breeders. One group shares their tank with 6 panda cory and has 3 PVC caves and two sponges for hiding space. The other group shares the tank with 12 Hyphessobrycon megalopterus, 3 Hyphessobrycon ocasoensis, 6 Cory oiapoquensis, and 2 Otocinclus macrospilus. The set-up is the same in the second tank with only two differences. There is only one cave, and that tank is overgrown with Najas guadalupensis. Both are also on the same central system, so water quality doesn't vary much between them.

Amazingly, even though it is substantially more heavily stocked, the fish in with the tetras have grown substantially faster. Both groups were about 1-1/2 inches SL when I got them early March. Those with the three caves are now about 2 inches SL. The ones with the overgrown jungle average 2-1/4 inch SL and are out in view a lot more often (dithers vs. cover is another question to be asked). Regardless, there's an obvious size difference.

There's a lot more to take into consideration than just the water

Larry

[MatsP]

Amazingly, even though it is substantially more heavily stocked, the fish in with the tetras have grown substantially faster. Both groups were about 1-1/2 inches SL when I got them early March. Those with the three caves are now about 2 inches SL. The ones with the overgrown jungle average 2-1/4 inch SL and are out in view a lot more often (dithers vs. cover is another question to be asked). Regardless, there's an obvious size difference.

There may also be differences in feeding between the tanks - even if the food intended for the plecos is identical, there may be some other differences.

I think unless you have broodstock that come from the same parents, under otherwise the same conditions and only change one thing at a time, it's terribly difficult to compare. I have certainly seen the scenario where I've moved a few smaller fish from a fry-tank to a larger tank, and kept the rest in the original fry tank. The ones that have moved will definitely "spurt" and grow much faster than those in the fry tank. But there are of course several differences beside the obvious "the fish is in a bigger tank" difference - feeding and water quality is certainly SOME of that difference, but far from the whole story.

--
Mats

[PseudaSmart, posts: 180]

Thanks for proving me right about the discussion part!
Guys, please send me some data. Without it we are still working with 'voodoo and tribal knowledge'. Without going into detail I have spent my career making order out of chaos and solving impossible problems. I doubt I will be able to model fry growth rates but I will find some interesting trends - if I get data.

I prefer to listen to other people rather than talk but it in this case it is important to know that I have kept tanks for over 40 years and have spawned many species from the top to the bottom of the water column.
Thanks,
Jim

[Shane]

Guys, please send me some data. Without it we are still working with 'voodoo and tribal knowledge'.

I think the data you are looking for is, for the most part, already out there. You will just need to do the legwork to find it and collate/summarize it in a way useful to aquarium hobbyists. I would incorporate, but be careful, with hobbyist derived information vice that sourced to controlled scientific experiments.
-Shane

Here are a few starting points I found

The effects of stocking density, prey concentration and feeding on Rhinelepis aspera (Spix & Agassiz, 1829)(Pisces: Loricariidae) larviculture
José Cláudio Epaminondas dos Santos1*, Marcelo Mattos Pedreira2 and Ronald Kennedy Luz3

Ontogenetic allometries and shape changes in the suckermouth armoured catfish Ancistruscf.triradiatus Eigenmann (Loricariidae, Siluriformes), related to suckermouth attachment and yolk-sac size
http://onlinelibrary.wiley.com/doi/10.1 ... edMessage=

Caloric density of Loricariichthys platymetopon (Osteichthyes, Loricariidae) in the Upper Paraná River floodplain, Brazil
http://www.scielo.br/scielo.php?pid=S15 ... xt&tlng=es

Reproductive behavior, development and eye regression in the cave armored catfish, Ancistrus cryptophthalmus Reis, 1987 (Siluriformes: Loricariidae), breed in laboratory
http://www.scielo.br/scielo.php?pid=S16 ... xt&tlng=es

Feast to famine: The effects of food quality and quantity on the gut structure and function of a detritivorous catfish (Teleostei: Loricariidae)
http://www.sciencedirect.com/science/ar ... 3309011246

Do wood-grazing fishes partition their niche?:
morphological and isotopic evidence for trophic
segregation in Neotropical Loricariidae
http://onlinelibrary.wiley.com/doi/10.1 ... edMessage=

I would also recommend checking out a few good "best pratcices" aquaculture papers as well as papers on non-loricariids that might be useful.

Simple indices for the assessment of the influences of social environment on growth performance, exemplified by studies on Arctic charr
http://www.springerlink.com/content/p10r6qr207733161/

Physiological and social constraints on growth of fish with special reference to Arctic charr, Salvelinus alpinus L.
Physiological studies of growth in animals predict that growth rates should decrease with increasing size, but when Arctic charr, Salvelinus alpinus, were reared together in large groups there was often a positive correlation between initial body size and the growth rate of an individual fish. This suggested that social interactions were important determinants of growth rates and, in the absence of the establishment of direct linear hierarchies, it is suggested that growth suppression is the result of short-term bouts of aggression associated with feeding periods leading to reduced food intake by certain fish. Evidence is presented to show that growth suppression can be reduced by increasing the frequency of feeding.
http://www.sciencedirect.com/science/ar ... 8685900110

Effect of feeding frequency on food consumption, growth, size variation, and feeding pattern of age-0 hybrid sunfish
Four treatment groups of age-0 hybrid sunfish (female green sunfish Lepomis cyanellus×male bluegill L. macrochirus) were fed to satiation at one of four frequencies (one, two, three or four meals per day) for 30 days. Fish fed three and four times daily showed the greatest consumption and growth rates; food conversion ratios did not differ among the four treatments (P>0.05). Because growth and food conversion were not enhanced when feeding was increased from three to four times daily, the optimal feeding frequency for growth was considered to be three times per day.
http://www.sciencedirect.com/science/ar ... 869800266X

Does light have an influence on fish growth?
Light compares a complex of external and ecological factors, including colour spectrum, intensity and photoperiod. Light characteristics are very specific in an aquatic environment and light is extremely variable in nature. `Receptivity' of fish to light profoundly changes according to the species and the developmental status. Specific photoreceptor cells are present in both eye and pineal. If it is easy to change the light in experimentation and to observe the effects on fish growth, it is much more difficult in nature to make such determinations. In larvae, many studies have been dedicated to the influence of intensity and photoperiod on growth: generally, species need a minimal threshold intensity to be able to develop normally and grow. This is probably related to the aptitude to localize, catch and ingest prey. Light is also indispensable for body pigmentation, an important phenomenon involved in early development and growth. Too intense light can be stressful or even lethal. A few species are able to develop and grow at very low intensities or, sometimes, in the absence of light. Generally, long daylength improves larval rearing quality.
http://www.sciencedirect.com/science/ar ... 8699000745

Chronic exposure of channel catfish, Ictalurus punctatus, to ammonia: Effects on growth and survival
The growth of juvenile channel catfish (Ictalurus punctatus) was reduced in a linear manner during a 31 day growth trial when exposed to concentrations of ammcnia ranging from 48 to 989 μg/l NH3N (0.31 to 5.71 mg/l NH+4N). On a wet weight basis, growth was reduced by 50% at 517 μg/l NH3N and the no growth occured at 967 μg/l. The no growth level was 60% of 96-h LC50 value. Mortality was increased significantly at 989 μg/l NH3N and above. The sublethal effects of ammonia may depend, in part, on the concentrations of NH4+ and and Na+ in solution.
http://www.sciencedirect.com/science/ar ... 8678900819

[dw1305, posts: 329]

Hi all,
I think this is a very interesting project. I don't know much about fry growth rates, but I have a lot of experience of water quality management and manipulation, from work on the biological re-mediation of landfill leachate (which is analogous to uber-polluted tank water).

The set-up is the same in the second tank with only two differences. There is only one cave, and that tank is overgrown with Najas guadalupensis. Both are also on the same central system, so water quality doesn't vary much between them. Amazingly, even though it is substantially more heavily stocked, the fish in with the (plants) have grown substantially faster. ..... (dithers vs. cover is another question to be asked).

You can't conclude that water quality doesn't differ between the tanks, actively growing plants are probably the most important single factor in improving water quality, as well as the plants providing additional surfaces for biofilm development etc.

Even if the water is then circulated through other tanks, the plants are an order of magnitude more efficient at ammonia (NH3) removal than filter bacteria, and the tank with the plants in will have lower NH3/NO2/NO3 levels. This tank will also have enhanced oxygen levels during photosynthesis.

As well as water quality the other factor is the one that Shane has posted in the links to the Salvelinus and Lepomis papers, if the fish are out and about more, in a non-stressful environment with high quality water, they may be feeding more frequently.

cheers Darrel