Backyard Aquaponics
A place to discuss aquaponics

Hey All,

I'm wondering how many gold fish my system can support/requires. I have a 150 Gal FT and its a CHIFT PIST (150 Gal ST). And 2 grow beds that measure 8' x 3' with close to 12'' grow media.

Basic question - How many fish should I start my system with. I know gold fish are pretty small so I wasn't quite sure.

Any information would be helpful. Thanks

A lot. I have ~50 3" comets in 400 gallons and 72 square feet of 8" media, and they're not nearly enough. Every plant over 8" is fighting major deficiency (not quite green pallor and shriveling brown edges, I add some organic garden fertilizer but can't seem to overcome it). I grow lettuce great tho

Try getting a better quality feed perhaps Chris...

Were you just starting with goldfish and then replacing them sugarbeard, or growing full time with them..?

earthbound - I am starting with gold fish, but plan to grow with them for at least the next year before possibly trying something like tilapia.

I will be firing up my system for the first time this week.

Here is a site that gives the number of goldfish per pound depending on the size of the fish. From there you can calculate how many fish using the "rule of thumb" of 1 pound of fish for each 2.5 to 5 gallons of fish tank volume max.

http://www.ozarkkoi.com/Goldfish-Weight-Goldfish-Information-sc-97.html

Given a 150 gallon fish tank can support 30 - 60 pounds of fish, and 3" goldfish total around 50 per pound, you could stock 1500 - 3000 goldfish initially. They will grow to about 5-6 inches in a year so realistically you'd be able to stock 240 - 720.

Realize that the rule of thumb is for maximum density. My system has a 250 gallon fish tank, two 3 foot by 6 foot grow beds, around 250 - 300 goldfish, and it provides more than enough nutrients.

yikes...
that's way overstocked.. in an ap system, you should base the number of fish on the amount of filtration, not the size of the ft..
a good "rule of thumb" is 20 to 25lbs of (grown out) fish for every 100 gallons of filtration

+1 keith

Based on your wet gravel I would say your system should support about 30 lbs of finished fish. So in general I would say stock 30 fish (like tilapia) as you would harvest them at about 1 lb each. The system may be a little deficient in the beginning but the fish would grow into it.

However, you will be stocking goldfish for one year so you could do a bit more to start (max 50 or so) to get things going but I think I would just start with 30. You can always add more fish if you find your system needs them. Removing them can be inconvenient for your fish and pocket book.

I did say "rule of thumb" and "max" . . .


Anyway, Nate Storey has a short video on the topic:



https://www.youtube.com/watch?v=IPEFlhRBaQI

His rule of thumb is 1 pound of grown out fish for every 8 - 10 gallons of water. The OPs grow beds are around 180 gallons of volume each (3' x 8' x 1' x 7.48 gallons/cubic foot), so he has plenty of filter capacity for his 150 gallon fish tank.

Given Nate's rule of thumb you're looking at 15 to 18.75 pounds of fish. And given a size of around 5 - 6 inches within a year for the goldfish, you're looking at a stocking density of 120 to 225 fish.

Given Keith's rule of thumb and rounding off to a 2:1 GB to FT ratio of 300 gallons of grow beds, you're looking at 60 to 75 pounds of fish. That's starting to exceed the original rule of thumb I proposed.

Given my experience in my system with goldfish, and Nate's rule of thumb, I'd like to propose a new rule of thumb of 1 gold fish per gallon as a good start provided you have sufficient filtering.

i didn't notice that there were 2 gb's, i calculated 1 at about 80 gallons or so
and goldfish grow much quicker than you'd expect.. if you start with 1" fish, they can be close to 1lb in 1 year

Feeder goldfish at the pet store are around 1/2" - 3/4" and cost around 11 - 22 cents each. With water temperatures averaging 90 degrees F in the summer and 45 degrees F in the winter, and feeding them twice a day, they grow to around 5 - 6 inches in length within a year. It takes eight 6" goldfish to weigh a pound, and twelve 5" goldfish to weigh a pound. Not sure how long a single goldfish is when they reach a pound as mine haven't gotten anywhere near that size yet . . .

Dang it! I did the same thing! Sorry multiply my answer by two...

I meant (8 X 3 X .8 (10in depth) X 2 (num of beds) X 7.4) / 5 = 56 lbs grown fish...

Sorry for the confusion.

JeffB - I agree that this is not a perfect calc when talking about very small fish. I cycled my 1000gal system with 120 goldfish... I did add a little ammonia to get things moving but after I started seeing ammonia the gold fish did the rest. I have 100 tilapia from 2" to 4" now and I run a 20ppm nitrate almost constant.

Yes you did but that's not necessarily good advice Jeff. A person starting out should be given conservative advice so that they don't overstock and have a fish die-off. Rather let them start out understocked and then they can tweak their system for best results.

Regards, Martin,

Seems this topic has been discussed before, and it too included not necessarily good advice: http://www.backyardaquaponics.com/forum/viewtopic.php?f=12&t=6646&hilit=rule+of+thumb

There are seven pages of posts in there, care to be a bit more specific?

First paragraph of the first post: