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Another Ratio Thread
http://www.backyardaquaponics.com/forum/viewtopic.php?f=11&t=5023
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Author:  RupertofOZ [ May 4th, '10, 21:42 ]
Post subject:  Re: Another Ratio Thread

Many members will attest to readings of 0,0,0 ... :wink:

Author:  hydrophilia [ May 7th, '10, 21:54 ]
Post subject:  Re: Another Ratio Thread

I still like to have a little left on the plate to show me that the plants have gotten all they need. Zero is fine if the plants are getting all they want, but I can seldom tell until they are in deficit.

Author:  TCLynx [ May 8th, '10, 01:37 ]
Post subject:  Re: Another Ratio Thread

No you don't need high Nitrate levels. And if you have a good pH and balance of the trace elements and potassium needed, you can probably get your nitrate levels way low and have excellent plant growth. My nitrates tend to stay a bit high and I struggle with Iron because of my high pH (due to shells as media.)

Having excess water in a system (like in a sump tank) doesn't mean the nutrients are more diluted necessarily. It just might take a little bit longer to reach a good balance. It will also mean that once things are stable, they will tend to remain more stable. (Think of it a little like thermal mass, it might take a bit longer to get a house with lots of thermal mass to your desired temperature but once it is there, it takes far less energy to keep it stable.)

Author:  BNDYBEAR [ Apr 17th, '11, 18:20 ]
Post subject:  Re: Another Ratio Thread

been doing some ratio calculations today to make sure I am within my paramiters.
I understand GB:FT = 2:1 although my system is more like GB/1000lt:FT/1200lt (sump 1000lt) lets call it 1:1!

I also understand GB volume needs to be enough to handle stocking density and the figures of 30kg:1000ltFT have been discussed as safe parameters when system ratio is 2:1.
This would mean 30kg of fish per 2000lt of GB......

Given that my GB volume is 1000lt I am working off no more than 15kg of fish in my system.

Currently I have approx 30 SP 50-120mm in FT1 (600lts).
Also have 50 trout fingerlings 50-75mm in FT2 (600lts).
I also have 25 trout fingerlings in ST but will be removed to farm dam at approx 150mm in size

So.... 80 fish at 15kg per 1000lt GB would mean my fish (if they all grow at the same rate) would be starting to push the boundries of my filtration at 187grams.

Given that the SP will put on minimal wieght over the next 6months I would say my trout could all get to approx 200grams before my system is getting close to danger zones. and thats within the safe paramaters!

Obviously they will not all grow at the same rate and I will be harvesting as soon as the first trout are 200g.....


Am I on the right track or have I missed something in terms of ratios????

Author:  freoboy [ Apr 17th, '11, 18:52 ]
Post subject:  Another Ratio Thread

BNDYBEAR wrote:
been doing some ratio calculations today to make sure I am within my paramiters.
I understand GB:FT = 2:1 although my system is more like GB/1000lt:FT/1200lt (sump 1000lt) lets call it 1:1!

I also understand GB volume needs to be enough to handle stocking density and the figures of 30kg:1000ltFT have been discussed as safe parameters when system ratio is 2:1.
This would mean 30kg of fish per 2000lt of GB......

Given that my GB volume is 1000lt I am working off no more than 15kg of fish in my system.

Currently I have approx 30 SP 50-120mm in FT1 (600lts).
Also have 50 trout fingerlings 50-75mm in FT2 (600lts).
I also have 25 trout fingerlings in ST but will be removed to farm dam at approx 150mm in size

So.... 80 fish at 15kg per 1000lt GB would mean my fish (if they all grow at the same rate) would be starting to push the boundries of my filtration at 187grams.

Given that the SP will put on minimal wieght over the next 6months I would say my trout could all get to approx 200grams before my system is getting close to danger zones. and thats within the safe paramaters!

Obviously they will not all grow at the same rate and I will be harvesting as soon as the first trout are 200g.....


Am I on the right track or have I missed something in terms of ratios????

If you harvest early like you said and maybe run cd you should be ok I think :?

Author:  TCLynx [ Apr 17th, '11, 21:27 ]
Post subject:  Re: Another Ratio Thread

Your water tests will tell. Keep a close eye on water quality, and to keep trout good, you want to make sure that you are not getting any solids or uneaten feed build up in the fish tanks. What are your flow rates like? Make sure you are turning over the volume of your fish tank plenty since circulation and dissolved oxygen are very important to trout. This may mean your grow beds wind up getting more water than they would prefer but it is a good way to keep water quality high for the fish. The biggest danger when pushing the limits as you may see will be that too much solids building up in grow beds might become evident so make sure you have a large amount of worms and just carefully monitor water quality and reduce feed/pump more if there are spikes and that will be an indication of when you need to really get on to harvesting some fish. Make sure you have plenty of aeration for the trout.

Author:  earthbound [ Apr 18th, '11, 10:46 ]
Post subject:  Re: Another Ratio Thread

Yeah, pushin things a bit there....

Man, I go completely the other way, I'm enjoying pushing a system as to how much you can make things grow with only a few fish.. My 4 bed at home only has about 15 silvers in it, I've just replanted the whole system and now I'm feeding the silvers 3 times a day, pumping them hard to see what sort of growth I can get from only a few fish.

Author:  RupertofOZ [ Apr 18th, '11, 15:24 ]
Post subject:  Re: Another Ratio Thread

Yep, people totally over estimate the amount of fish necessary for plant growth... and usually totally overstock their systems in relation to their filtration....

A 300 - 400 gm trout is a good feed.... a 200 gm trout is a snack....

Author:  mantis [ Apr 18th, '11, 17:22 ]
Post subject:  Re: Another Ratio Thread

RupertofOZ wrote:
Yep, people totally over estimate the amount of fish necessary for plant growth... and usually totally overstock their systems in relation to their filtration....

A 300 - 400 gm trout is a good feed.... a 200 gm trout is a snack....


But I bet you would also order the mains serve at fasta pasta :laughing3:
We were at one last night and we got entree serves and couldnt finish them, and I saw the mains serves coming out :shock:

Author:  Russell_Vic [ Mar 14th, '12, 14:26 ]
Post subject:  Re: Another Ratio Thread

A question on the ratio of Pump Capacity : FT volume. I've read that you should size your pump to change the fish tank volume at least once per hour, but is there a top limit? I am planning my first system to be made from 200 litre plastic barrels, one for the FT, 2 cut in half for 4 GB, and one sump. The pump i'm looking at is a 12v bilge pump rated at 360GPH (1380 litres/hour), if it comes close to its specs it will change the FT volume in just under 9 minutes. I could restrict the flow, but what would be a reasonable target ?

Author:  arbe [ Mar 14th, '12, 16:18 ]
Post subject:  Re: Another Ratio Thread

The bilge pump rating will be at 0 head. How much head will you have and how much will it be able to pump?

Also, I dont think Bilge pumps are really all that good for constant use.

Author:  RupertofOZ [ Mar 14th, '12, 17:09 ]
Post subject:  Re: Another Ratio Thread

Yep, nearly everyone that's tried to run a 12v bilge pump constantly.. has found they burn out in only a few months...

Author:  Madcap [ Mar 14th, '12, 17:48 ]
Post subject:  Another Ratio Thread

RupertofOZ wrote:
Yep, nearly everyone that's tried to run a 12v bilge pump constantly.. has found they burn out in only a few months...

or block more easily in my experience...

Author:  Russell_Vic [ Mar 15th, '12, 08:08 ]
Post subject:  Re: Another Ratio Thread

Thanks for the warning on bilge pumps. I have checked specs on some other pumps and volume drops off dramatically with head height, I need to do some measuring and calculate the actual head, I am guessing around 1.0 to 1.2 metres.

So when I source a pump, should I aim to change the FT water 1-2 times per hour ?
Is 3-4 times an hour better ?
Some people must have experimented with different fill and drain times on their grow beds - is this more critical than water changing rate in the fish tank ?

Author:  4xjbh [ Mar 15th, '12, 08:35 ]
Post subject:  Re: Another Ratio Thread

Change FT water at least once per hour, if you happen to do any more there is no harm, depending on the setup the solids will be kept on the move (out of FT). As well as the head don't forget to also allow for possible expansion, so if you are actually changing the water 3-4 times per hour the pump has that capacity to expand the system, but will probably drawing more wattage.

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