RTC growth slowed down drastically after 1st year

[Drstrangelove]

Their sizes are roughly 14'' & 16'' now. I feed 3 times a week with white fish fillet and frozen shrimps and sinkingpellets.

Is there any recipe for faster growth?

Not to ignore the WC, tank size, nitrate or nutrient issues which are important and possibly decisive, let's tackle the underfeeding issue as well if you want. Measure out what you normally feed the two RTC (together, not individually) in total.

E.g., one meal normally equals: 6 ounces of white fish, 4 ounces of shrimp, 1 ounce of pellets. OR, one meal is 10 ounces of white fish, while another is 10 ounces of shrimp while the other is 6 ounces of pellets. If you don't do them that way, describe what you think they get each week on average by weight.

By the way, which pellets are you using?

If other fish are also eating the same food, you'll have to estimate how much the 2 RTC are together eating in total for each feeding.

It's possible to convert the food weight to dry content protein and energy equivalent and to compare that to their projected body weight to determine how much of a surplus diet they have. Without a surplus, many fish won't keep growing.

Also, are your other fish also not growing quickly?

 

[Jamal Haidar]

Does Kuwait fortify the disilled water? And if they do, the water may be missing key minerals. Using a water mineral supplements wouldn't hurt.

The water desalinated but it's not 100% distilled water, certainly it's fortified but I do not know to what extent. I addition, I do add API salt to the water to improve gill function.

 

[Jamal Haidar]

Not to ignore the WC, tank size, nitrate or nutrient issues which are important and possibly decisive, let's tackle the underfeeding issue as well if you want. Measure out what you normally feed the two RTC (together, not individually) in total.

E.g., one meal normally equals: 6 ounces of white fish, 4 ounces of shrimp, 1 ounce of pellets. OR, one meal is 10 ounces of white fish, while another is 10 ounces of shrimp while the other is 6 ounces of pellets. If you don't do them that way, describe what you think they get each week on average by weight.

By the way, which pellets are you using?

If other fish are also eating the same food, you'll have to estimate how much the 2 RTC are together eating in total for each feeding.

It's possible to convert the food weight to dry content protein and energy equivalent and to compare that to their projected body weight to determine how much of a surplus diet they have. Without a surplus, many fish won't keep growing.

Also, are your other fish also not growing quickly?

I feed them less than what you mentioned. The amount is one meal 6 ounces white fish + 1 ounce pellets and the other meal is 6 ounces shrimps + 1 ounce pellets (the amount for both RTCs). I alternate between the 2 meals for 3 times a week. And I don't know how to estimate the dry weight.

The pellets are new life spectrum water stable disks.


I have one more pacu that I feed him the same pellets and Hikari pellets but his growth is ok.

I am planning to increase the amount once I move the 2 RTC'S to the 550 gallons tank.

 

[Drstrangelove]

I feed them less than what you mentioned. The amount is one meal 6 ounces white fish + 1 ounce pellets and the other meal is 6 ounces shrimps + 1 ounce pellets (the amount for both RTCs). I alternate between the 2 meals for 3 times a week. And I don't know how to estimate the dry weight.

The pellets are new life spectrum water stable disks.
View attachment 1128834

I have one more pacu that I feed him the same pellets and Hikari pellets but his growth is ok.

I am planning to increase the amount once I move the 2 RTC'S to the 550 gallons tank.

Okay, I calculated that amount:

per week:

1) 3 x a week: 1 oz pellets @ 90% dry weight = 76.4 grams
2) 1.5 x a week: 6 oz white fish @ 35% dry weight = 89.2 grams
3) 1.5 x a week: 6 oz shrimp @ 40.7% dry weight = 103.8 grams.

Total 269.4 grams per week or 38.5 grams per day

The estimated weight of a well fed 16" and 14" RTC totals 3.36 lbs or 1,522 grams.

The diet works out to 2.5% dry weight food to body weight, which is a bit more than 15 inch, 2-lb channel catfish are fed for optimal growth in fisheries. I think your feeding at this point is probably not the reason you are seeing no growth.

However, just to be sure, note that using the feeding schedule and assuming a feed conversion ratio of 2, it would take 5 weeks to see a 2 inch gain (14" to 16"), and 2.5 weeks to see a 1-inch gain. I wonder if people that grow their RTC faster than yours are feeding at a higher rate.

I'm not saying that it's healthy, just pointing out what the numbers are saying.

 

[Jamal Haidar]

Okay, I calculated that amount:

per week:

1) 3 x a week: 1 oz pellets @ 90% dry weight = 76.4 grams
2) 1.5 x a week: 6 oz white fish @ 35% dry weight = 89.2 grams
3) 1.5 x a week: 6 oz shrimp @ 40.7% dry weight = 103.8 grams.

Total 269.4 grams per week or 38.5 grams per day

The estimated weight of a well fed 16" and 14" RTC totals 3.36 lbs or 1,522 grams.

The diet works out to 2.5% dry weight food to body weight, which is a bit more than 15 inch, 2-lb channel catfish are fed for optimal growth in fisheries. I think your feeding at this point is probably not the reason you are seeing no growth.

However, just to be sure, note that using the feeding schedule and assuming a feed conversion ratio of 2, it would take 5 weeks to see a 2 inch gain (14" to 16"), and 2.5 weeks to see a 1-inch gain. I wonder if people that grow their RTC faster than yours are feeding at a higher rate.

I'm not saying that it's healthy, just pointing out what the numbers are saying.

Thanks Drstrangelove for the detailed calculation. Can you please provide links where I can read more about how to estimate growth rate and how to make sense out of food to body ratio.

 

[Drstrangelove]

Thanks Drstrangelove for the detailed calculation. Can you please provide links where I can read more about how to estimate growth rate and how to make sense out of food to body ratio.

There are dozens and dozens of articles online about these topics, but here are few for example:

http://www2.ca.uky.edu/wkrec/RVWFeedPractice.htm
http://www.scribd.com/doc/56210094/2/THE-RELATIONSHIP-BETWEEN-FOOD-INTAKE-AND-BODY-WEIGHT
http://www.planta.cn/forum/files_pl...opulation_of_fish_in_the_river_thames_397.pdf
http://www.aces.edu/dept/fisheries/aquaculture/documents/guidetocatfishfeeding.pdf
http://www.nap.edu/openbook.php?record_id=950&page=20
http://www.fao.org/docrep/x5738e/x5738e03.htm

Growth rates for RTC can be found here on MFK as people often post and ask about that topic. There's a very recent thread in fact, but you can simply search for that using the search function.

MFK threads are useful as they include many people like yourself.

Fastest growth is not of course the same as healthiest growth. Animals in fisheries are not fed to produce a long-lived, attractive, happy pet, but a high profit, quick to slaughter piece of food to sell. However, the people who study growth rates and feed rates in that industry are the most prominent available. Feed conversion ratios (FCR) are common in all food industries, fishing being just one.

Fish body weight (and indirectly food requirements) are derived from calculations of fish length and girth. Each species of course is different as a 2 foot eel obviously has a different girth than a 2 foot RTC, and thus it's weight will be very different. But 'within' a species, length is more predictive if girth is similar in a relative basis.

 

[thebiggerthebetter]

Nice, Drstrangelove. Many thanks for the education.

I think your feeding at this point is probably not the reason you are seeing no growth.

Agreed. Both the quality and the amount sound good, albeit I personally would reduce the shrimp offering by 2x and increase the white fish by two and also once in a while diversify. Offer algae disks, or fish heads (I assume white fish is headless?), different fish, better whole, worms, insects, reptiles, amphibians, etc.

 

[raubiy]

Nice, Drstrangelove. Many thanks for the education.



Agreed. Both the quality and the amount sound good, albeit I personally would reduce the shrimp offering by 2x and increase the white fish by two and also once in a while diversify. Offer algae disks, or fish heads (I assume white fish is headless?), different fish, better whole, worms, insects, reptiles, amphibians, etc.

Thebiggerthebetter whay fish head play role. I saw some guys on youtube cut off head and feed. I'm doing same thing.
Nutrition and this thing's are in head?
Thebiggerthebetter help me with this one. I was thinking head is bad for fish because those guys on Youtube...

 

[thebiggerthebetter]

What guys on YouTube? I am looking to learn too.

In general, we strive to mimic how the fish feeds in the wild where we reasonably and affordably can. Vast majority of predators swallow their prey whole - head, tail, sharp spines, skin, scales, guts, feces, exoskeletons, claws, and all. Besides, it is understood that e.g. fillet are almost all protein, not a significant source of vitamins, minerals, microelements, enzymes, co-factors, and a sleuth of other biologically active and nutritionally necessary components (hence, the need for good quality pellet or a vitamin presoak). Whole fish is a different matter, even though it is not offered alive, its nutritional composition is close to what the predator gets in the wild. Their stomachs have a tough lining and can handle all kinds of abrasive and sharp features of their natural prey. Sure, there are accidents but these are rare.

Wholesome diet is good for humans too. Highly processed is not so.

 

[Jamal Haidar]

Nice, Drstrangelove. Many thanks for the education.

Agreed. Both the quality and the amount sound good, albeit I personally would reduce the shrimp offering by 2x and increase the white fish by two and also once in a while diversify. Offer algae disks, or fish heads (I assume white fish is headless?), different fish, better whole, worms, insects, reptiles, amphibians, etc.

I agree with thebiggerthebetter to diversify. I will also try whole fish, frozen tilapia possibly. But are insects, reptiles and amphibians safe? Is there any disease risk?