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Sump & fishtank volumes vs stocking rate
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Author:  jimmy_d_ward [ Jan 16th, '08, 13:35 ]
Post subject:  Sump & fishtank volumes vs stocking rate
If I have a 500L fishtank and a 500L sump (without fish in it), can I stock the fishtank as though it was a 1000L capacity tank operating without a sump because the overall water volumes, and hence overall ammonia concentrations, would be equivalent? How quickly does ammonia build up in the fishtank between pumping cycles?

And, how would the equation change if I put yabbies in the sump? Is 1kg of yabbies considered roughly equivalent to 1kg of fish? i.e. 1kg of yabbies in the sump means 1kg less fish being stocked in the fishtank...

Just trying to optimise the use of my 3x 500L tanks.
Author:  RupertofOZ [ Jan 16th, '08, 13:40 ]
Post subject: 
Quote:
If I have a 500L fishtank and a 500L sump


Quote:
Just trying to optimise the use of my 3x 500L tanks.


Please clarify Jimmy..... do you have 2 x 500ltr tanks or 3 x 500ltr tanks???
Author:  KudaPucat [ Jan 16th, '08, 13:56 ]
Post subject: 
jimmy for safety's sake with a new system I'd disregard the volume of the sump in your calculations.
But in Theory you can stock to the total volume in the entire system. However I do not recommend it.
Author:  jimmy_d_ward [ Jan 16th, '08, 14:03 ]
Post subject:  Re: Sump & fishtank volumes vs stocking rate
My original post didn't make a lot of sense!

I do actually have 3 tanks, and will intend to eventually use 2 as fishtanks and the third as a sump/yabbie tank. To begin with, it will be one FT and one S/YT.

If I take your advice and don't include the sump volume in the calcs, then how should I account for the yabbies?

Suppose I choose 2kg per 100L as my 'newbie' stocking density, which gives me up to 10kg of fish in my fishtank (I'd call this 20 fish, harvesting the first one when it reaches 500g). If I was to shoot for 2kg of yabbies in the sump tank, it'd probably mean >100 yabbies, which I expect is not really feasible for humane reasons, so I think I've answered my own question... :roll:
Author:  KudaPucat [ Jan 16th, '08, 14:07 ]
Post subject: 
If you disregard the sump in your calcs, personally I don't think you'll have enough yabbies to cause you any grief.
They are territorial, and unless you make lots of hideyholes and extra levels you wont get more than maybe 12 in an IBC, 15 at the most. They tend to like 300mx300m each but will survive on less if there's a couple of rocks.
This many yabbies wont be much of a drain on the 1000L sump, so ignore them.
fit your fish to the other 2000L you have, which is 120kg of fish at ABSOLUTE maximum stocking. so 120 Fish should be your starting maximum imho.
this should be safe if you test regularly and have sufficient growbeds
Author:  RupertofOZ [ Jan 16th, '08, 14:12 ]
Post subject: 
Jimmy I'd disregard the sump tank capacity altogether....

Do't think you'd be starting your system with the sump and fish tank full would you, unless maybe you were using both tanks from the start :wink:

As long as you're going to add the second tank before the fingerlings get to much more than 250-300gms then I think you could stock to the capcity of both the fish tank volume....

@2kg/100 with a total of 1000ltr .... 20kg of fish > 40 fish to 500gm size...

Stock the yabbies in the sump tank... yep they produce ammonia but I don't think you need to incorporate it into calculations.... they're slow growing...

If you're going to add the second tank later, you could always go for 20 fish now and add another 20 into the second tank when you bring it online :D
Author:  jimmy_d_ward [ Jan 16th, '08, 14:20 ]
Post subject: 
Thanks for the tips, guys!

Will shoot for 2kg/100L as a start = 20 fish in one tank, a dozen yabbies in the sump with lots of hiding places.

I'll add the second fishtank + 20 more fish when first lot are half-grown, and will aim to always keep two sizes of fish, in separate tanks.

As I get good at AP (and I hope to), then when I've harvested the fish from tank #1, I can re-stock with, say, 30 fish. Then re-stock T2 with 40, then T1 with 50, and eventually in a few years, I'll be running at maximum density of 60 fish in each tank (i.e. 6kg/100L).
Author:  RupertofOZ [ Jan 16th, '08, 14:32 ]
Post subject: 
Quote:
I'll be running at maximum density of 60 fish in each tank (i.e. 6kg/100L)


Don't even try Jimmy.... even with a growbed ration of 2:1 :shock:

A 500ltr tank just doesn't allow for any margin for error IMHO

You keep coming back to this 6kg:100ltr ration stocking density... where did you get your infromation from that this is an (easy) stocking density to aim for????
Author:  RupertofOZ [ Jan 16th, '08, 14:35 ]
Post subject: 
6kg/100ltr > 60 x 500gm fish in 500ltr :shock:> 1 x 500gm fish in 10ltr of water (5 milk bottles)....

Visualise this and extrapolate how quickly your ammonia and nitrite level will/could rise to a point of toxicity with that volume.
Author:  KudaPucat [ Jan 16th, '08, 17:36 ]
Post subject: 
Rupe: See above
I quoted it as an absolute maximum at the start of this thread, and then suggested half that.
Which is where he's getting the 120 fish maxium.
Perhaps I wasn't clear enough. he seems to be thinking 60 fish = 60 kg per tank.
Jimmy, 6kg/100 is an ABSOLUTE you have to be damnably good, and most ppl here on the forum don't stock that high.
I said 60 fish, but meant grown to the 500g mark.
At 60 fish per tank, you'll not be able to have a 'set and forget' system like you have hinted you'd like.
To start with, until you become savvy, you will only want 20 fish per tank, on this I also concur with Rupert.
think about it this way. If you manage to have 120 fish in your tank, that's 1 every three days to harvest, or 2-3 per week. How many fish are you going to eat? 3 fish will feed two people happily. Will you eat fish as much as once a week? I know I don't atm.
Also think about harvesting. 20 now, and 20 in 6 months will allow an even harvest year round, empty 1 tank then the other, filling each with new fingerlings as it is emptied.
That give s a good feed every month. Then, when youhave an established system, maybe move to 40 per tank, and see how that goes... and so on.
Author:  Amacafish [ Jan 16th, '08, 22:08 ]
Post subject: 
In fact 60kg/1000L is a normal ratio for recirculating aquaculture systems you could but you would have to adapt a proper biofilter, UV lamps, degasing devices, O2 injection systems, failure alarm, I think that you would have more water filtering devices than fish tank and growbed.

I'll tell just for the dream that the new barra farming recirculating systems plan on 120 kg /1000L for a normal ratio and some people can produce clarias catfish up to 650 kg/1000L, just to keep'em wet. But there is no way you can have proper fish coming out that kind of system...

Good luck with the start J and stay low and increase with experience (just like a car, if you want it to go far keep calm the first one or two hundred thousand kilometers then you know when it copes with the speed or not)

Amacafish
Author:  RupertofOZ [ Jan 16th, '08, 22:23 ]
Post subject: 
Amacafish wrote:
In fact 60kg/1000L is a normal ratio for recirculating aquaculture systems you could but you would have to adapt a proper biofilter, UV lamps, degasing devices, O2 injection systems, failure alarm, I think that you would have more water filtering devices than fish tank and growbed.


Thanks Amacafish, I think this is what people often forget... they read somewhere in a aquaculture magazine that a RAS system is stocking 60kg/1000ltr (6kg/100ltr) and think that it is achievable in the backyard.

What the articles don't mention is, as you say, " proper biofilter, UV lamps, degasing devices, O2 injection systems, failure alarms", (added) and constant supervision by highly trained operators

Such systems are closely monitored and tested by experienced personel.

Not only is the equipment used highly expensive but sometimes also highly fragile... many an operation is so close to the limit that a power failure or stress related disease can wipe out a tank of fish in 30 minutes.

As you say, even in the best circumstances "you would have more water filtering devices than fish tank and growbed"......

Just not practical for the backyard operator.

And yep, I've heard of operations running levels of up to 200kg/1000ltr +..... I think they're called "canneries" :lol:
Author:  jimmy_d_ward [ Jan 17th, '08, 08:50 ]
Post subject: 
Thanks everyone, point taken. :?

The 6kg/100L figure I think came from Joel's book but I can't confirm. I accept that it is to be taken as an absolute maximum, and now based on your advice, I think I will not aim for 6kg/100L EVER, and will instead aim for half of this, i.e. an all-out eventual maximum of 30 fish per tank @ 500g per fish.

I will begin with 20 fish in 500L and will not increase this stocking density until I am very confident about my AP management.

For argument's sake let's say they take 6 months to get to 500g each. My plan would then be something like this:

0 months - 20 fingerlings in T1
3 months - 20 fingerlings in T2
6 months - 20x 500g fish harvested from T1 & replaced with 20 new fingerlings
9 months - 20 fish harvested from T2 & replaced with 20 fingerlings
12 months - 20 fish harvested from T1 & replaced with 20 fingerlings
etc

(Slower-than-expected growth would simply balloon this out to an 18-24 month cycle.)

If this system actually works for a year, I may choose to increase the next batch to 25 fingerlings, and do that for another year. That would equate to about 1x 500g fish each week, assuming they freeze well :D

If I get really excited and confident, I might increase to my (adjusted) maximum stocking rate of 30 fingerlings =3kg/100L.

Good point KP about potentially having too much fish to eat. Not worth overstressing a small system when enough is enough.

Thanks again for bringing me back down to Earth - much needed and appreciated.
Author:  RupertofOZ [ Jan 17th, '08, 09:02 ]
Post subject: 
Now that's a plan Jimmy, and a sustainable one :D
Author:  KudaPucat [ Jan 17th, '08, 11:50 ]
Post subject: 
oic, sorry Jimmy :oops: I made a blunder. :oops: When I said 120 Fish, I thought you had 2x1000L tanks, :oops:no wonder you and I were confusing one another. :oops: Yes 60 Fish per tank is too much, 30 is an great number to aim for :oops:
Humblest apologies, if you reread my posts, divide my recomended fish by 2 every time... :oops:
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