feed:weight ratios

[Allisyn Wood]

I've looked all over the internet and found TONS of information.  I'm lost in cyber-world.  I've searched the forum, but can't find the exact info I need, so I'm putting this question out there...

 

What is the feed rate to fish weight ratio? I realize this varies fish to fish, but as a general rule of thumb...?  (FYI, I'm using Aquamax 4000) The package says something like, 3-4 lbs of food per 100 lbs of fish over 4" per day... I can't figure out the math on this one partial because I don't know how much my babies weigh and don't want to put them the stress of a weigh-in.

 

For:

Catfish: general fingerling weights?  How much food per pound of fish?

 

Brim (similar to tilapia): weights per stages, and how much food/lb...

 

Currently giving them about 2 pellets per fish twice a day.  I think this is too much.  Can someone point me in the right direction? I have very small systems (40 gallon and 110 gallon). A 50 lb bag of food should last how long??

[TCLynx]

When growing out fish commercially, they often feed between 1-3% of total body weight daily depending on size.  Small fish usually get the higher % while bigger fish usually eat more like 1%.

 

However, I've never been willing to stress my fish out by weighting them unless I'm killing and eating them either so I just feed to satiation.

 

To do that.  I feed as much as they will completely consume in 5-15 minutes a couple times a day.

The key thing is to make sure there is no uneaten feed left over, if there is, reduce feeding next time and scoop out as much of the uneaten stuff as you can to keep from fouling the water.

 

For small fish, I tend to grind up the feed a bit in my grain mill so the little fish can handle the pellets.  I also tend to get a small (like 5 lb) bag of higher protein feed for the fingerlings when I first get them since small fish usually need higher protein levels and when that bag runs out I switch up to the Aquamax 4000. 

I did once get a 50 lb bag of Aquamax 400 grower that is higher protein but because of the high protein and oil it went bad before I could use it all but it is a nice small pellet size for the little fish.

[Allisyn Wood]

The aquamax 4000 is smaller pellets than what my fish breeder originally gave me so that's good for little mouths.  My catfish (<2") will come to the top and grab a pellet and swim around with it.  The brim just look at me while I'm out there, but the food will be gone later.  The little guys like it when I squish a pellet and drop in into the water, but sometimes the big guys come in for a mouthful, too.  Based on my Nitrate level yesterday (approaching 80) I think I am overdoing it.  Going to cut back to once a day for awhile and see.  Just wanted to see if there was a more exact ratio list for the different stages of growth. 

 

Which higher protein food do you use to start your fingerlings? At this point, probably won't switch them AGAIN, but for future reference...

 

BTW, since you're in the same zone as me, how does your feeding vary in the cold weather? I know you're all channel catfish.  Do they eat and fertilize your winter gardens or do you not bother with growing much in January - Feb, our freezing cold winter (LOL).  Can't wait til end of Oct!  It's HOT HOT HOT!

[TCLynx]

The feeding will slow down in cooler weather but so far I've noramlly still had plenty of nutrients to grow lots of cool/cold weather crops.  Things like broccoli, collards, kale, kohlrabi, cabbage all seem to like cold and there are many more things that like it cool but frosts may do a bit of damage like lettuce, beets, turnips, snow peas, spinach, etc etc.

 

I'm not sure the brand but I've gotten a 40 some % floating pellet from Aquatic eco in 5 lb bags for the fingerlings when I first get them.  The Aquamax 400 is also a good fingerling feed to start out with but I can't use a 50 lb bag up before it goes bad and I often get new fingerlings in 100 or 200 count batches so not worth it unless I can share a bag with about 5 other people since I think 10 pounds would be enough to then graduate the fish up to the 4000.

 

The fish will be ok with nitrate levels pretty high so I wouldn't panic about a nitrate level of 80.  Add more plants if you can.

[Allisyn Wood]

While I like the idea of "enough to get eaten in 15 minutes," I need some sort of mathematical/scientific chart to appease my mind...

 

So I found this:

Tilapia weights by week

 

If my sunfish were purchased in May as fingerlings, that makes them about  3-4 months (12-16 weeks).  According to this site, they about an average of 78 grams each (I think mine are smaller) so for 15 fish, they should get 1 to 1.25 oz of food per day at 2% of their weight. This looks like a lot... Much much MUCH more than I've been giving them and their filters are definitely dirty, so they're pooping a lot.

 

Am I doing this wrong???  Anyone out there got this down to a science?

 

[TCLynx]

It's a living ecosystem and though science strives to understand, I don't think nature always follows the rules.  That would be like expecting each and every baby to crawl at exactly the same age and deciding that any who crawled earlier or later were defective.

 

The feed % thing is what aquaculture does to make sure they are getting max growth with least waste from their feed since making money in aquaculture is a balance between growing the fish out to harvest size in the least amount of time possible while not spending any more money on feed than they have to while still producing an acceptable product.

 

So if you are not feeding the exact feed % that the aquaculturists do, it doesn't mean you are abusing your fish or anything.  And you can only feed as much as your filtration can support or you will be killing your fish with rising ammonia and nitrite levels.

Keep in mind that many aquaculture facilities will feed different types of feed at different stages of growth too depending on the type of fish and arrangement of the facility.

 

Also, a chart of weight by age might not be accurate if you are not growing the exact same strain of tilapia and feeding them by the same regimen and keeping them at the same temperature since all three of those will affect the growth rate.  Small fry and fingerlings will also grow slower if their early life is slowed by lower protein feed, less feed, or cool water.

 

So, If you want a measurement to work with, I would recommend feeding them as much as they will eat in 15 minutes and take note of how much that is.  You might need to measure out some amount of food like maybe 1 oz and then feed as much as they will eat in 15 minutes.  Basically feed a little bit and let them eat it and give them more and so on till they slow down or stop eating.  Then measure how much food you have left to figure out how much they ate.  Then you can slowly increase your feed amount from there while of course keeping an eye on ammonia and nitrite levels to know when you have gotten to the limit of your filtration.

[David Waite]

Allisyn in aquaculture or hatchery operations they do a 30 percent water change weekly. We dont have that option in aquaponics. The ratios you are looking at are for hatchery or large pond feeding operations. You really need to heed TC's advice on what they eat in 15 min vs a predermined weight. Keep it simple. Feed till they get satisfied twice daily and if your ammonia or nitrates get to high drop accordingly. Even large scale hatcheries will alter according to feed left on surface or spikes in ammonia or fish being off feed due to barometer or weather related issues. The 1 to 2 percent is optimum but no aquaculture operation runs that year round at all times. Just a thought to help you relax on percentages. Cant see your system so not sure why your filters are plugging up but if its a media system you should rework that part of your system.

Allisyn Wood said:

While I like the idea of "enough to get eaten in 15 minutes," I need some sort of mathematical/scientific chart to appease my mind...

 

So I found this:

Tilapia weights by week

 

If my sunfish were purchased in May as fingerlings, that makes them about  3-4 months (12-16 weeks).  According to this site, they about an average of 78 grams each (I think mine are smaller) so for 15 fish, they should get 1 to 1.25 oz of food per day at 2% of their weight. This looks like a lot... Much much MUCH more than I've been giving them and their filters are definitely dirty, so they're pooping a lot.

 

Am I doing this wrong???  Anyone out there got this down to a science?

 

[Allisyn Wood]

Hey guys,

 

Thanks for the peace of mind.  The link is actually from 'The essence of aquaponics" not a fish farm, so that's why I'm so worried I'm doing it wrong.  Most of the fish won't eat with me around, so I left probably 1/2 ounce for them this morning (much more than I've been giving them) and then came back about 20 minutes later with most still floating.  I think they like it soggy, especially the super wee guys, so I don't think they eat right away.  I ended up smooshing some for the itty bitty fish and scooping a lot out because I didn't want a mess on my hands. In the past, when I feed about 2-3 pellets per fish (this amount doesn't even register on my kitchen scale), it would be gone after 20-30 minutes.  I seem to have a recurring red mite issue which I'm guessing might be because there's not enough nutrients from lack of ammonia because of how little I've been feeding them, plus some of the fish don't look like they've grown at all.  Only about 4 ( out of about 15) are really getting big.  Supplementing with foliar maxicrop with iron on infected leaves.

 

I need to get a grinder.  This is probably part of my problem. Might help them eat faster.

 

My filter issues are at the intake inside the tank (no sump- straight to the gardens and then back to the fish as it's only 110 gallons) and I also have some mesh to catch solids at each outlet.  The one inside the tank gets coated pretty quickly.  They're not plugging up, just really dirty in a couple of days. I am using Beckett pumps with one of those 4" or so intakes inside a removable mesh sleeve. 

 

How often do you find you have to clean your filters? (My garden is only media beds, no raft.) I was hoping to get it down to once a week, but not sure this is realistic. 

 

Anyhoo... on with the trials.

[TCLynx]

Well I use a grate over my pump intakes that is big enough to let the pump suck up the food and fish poo but won't let my fish swim into the pump (my fish are not all that tiny.)  Anyway the grate is not needing cleaning unless I get leaves and such into the tank that will block it up.

 

Any sponge filter or fine mesh or screen will probably need very regular cleaning so as soon as your fish are large enough not to need it, you might switch over to something a bit more coarse so you don't have to clean it so much.

 

Yes, grind up some food.  You could probably put some in a bag and mash it between some boards or flat bricks if you don't have a coffee grinder or grain mill to make it a bit smaller for the little fish.

 

I doubt that the mites are due to lack of nutrients unless you get 0 nitrates on your test kit and the lower leaves of your plants are the ones yellowing first.  If you cycled up fishlessly first, there is normally plenty of nitrates left over for a while.

[Allisyn Wood]

Yes, I did a fishless cycle back in the early spring.  My nitrate levels were recently high(er) than normal (upwards of 80) but the ammonia and nitrites were 0.  Guess the mites are from the heat or something then, huh? So far, just effecting my newer tomato cuttings and yes, they do start from the bottom up.  Just spotted them today, so hopefully got a handle on them quick enough.

 

I'll definitely try your idea on mashing the food tonight.  Fingers crossed!

[TCLynx]

yea the little fish have trouble with food when it gives the impression of a fish swimming around with a beach ball stuck to it's mouth.  Mash up the food for a while and you will probably be on the right track after about a month to transition them back up to the full pellets.

 

Nitrates of 80 is a bit high so your plants are not suffering from lack of nitrogen.  Heat or other stress does tend to leave plants open to attack.

[David Waite]

Allison I clean my bucket about once a year in my ponds but I will clean it in my aquaponics system once every six months. It has been in 5 months and hasnt been cleaned once. Loose the little filter and let that material go to your media beds. You really just want to stop the fish from being sucked up and let all else go to the beds. Check out my system if it will help. If your pump is small you can use a plastic coffee container with a snap lid.

[Allisyn Wood]

Ahhhhh... I was thinking the idea was to keep the solids out of the pump...

 

I checked out your pictures and see what you mean about a bucket.  I will try the coffee container idea.

 

How often do you have to clean out your media beds when you allow the solids to run into them?

 

Cheers.