enough nutrients?

[darashee]

Hi,

i am getting alot of mixed messages from many sources, so I thought that I would come here where I can get a consensus of people already doing it..

in and aquaponics system (with murray cod) do i need to add anything for the plants? like chelated iron, potassium, phosphorus, seasol ~ anything, and how much

i haev a small system of 650 L - and am expecting the cod to arrive any day - and the system has been cycling for a while, and my nitrite is the only one still a 20. all the rest are down..

thoughts??

[Murray]

Over time you will need to add three in your list.
Iron needs to be added about once every two months.
The other two are added as buffers because the pH in recirculating Aquaponics systems tends to drift down over time.

Calcium in the form of hydrated lime and potassium in the form of a product called "Eco Rose" are useful pH buffers and at the same time adding those two elements.
I have not seen the need to add phosphorus.

Seasol is used as a general system tonic. Being seaweed based it has all sorts of minerals and trace elements naturally, and does not harm the fish.

[Outbackozzie]

Definately agree.

[Crusty]

At the risk of flames my direction, I will caution the use of calcium hydroxide in conjunction with any fish production unless it is being used to sterilize tanks or substrate that do not have aquatic animals in it. It is highly toxic to fish through its pH level (basically, it will burn them) and not that friendly to work with yourself.

If you were combining the two as a buffer, the plant cells will buffer with potassium bicarbonate and the soil will benefit from some form of lime (not hydrated). It may be beneficial to apply calcium carbonate or magnesium carbonate or even gypsum (quite possibly sodium bicarbonate will work) in place of the calcium hydroxide to err. on the safe side, if inexperienced in water chemistry and fish.

[Jason Palenske]

At the risk of flames my direction, I will caution the use of calcium hydroxide in conjunction with any fish production unless it is being used to sterilize tanks or substrate that do not have aquatic animals in it. It is highly toxic to fish through its pH level (basically, it will burn them) and not that friendly to work with yourself.

If you were combining the two as a buffer, the plant cells will buffer with potassium bicarbonate and the soil will benefit from some form of lime (not hydrated). It may be beneficial to apply calcium carbonate or magnesium carbonate or even gypsum (quite possibly sodium bicarbonate will work) in place of the calcium hydroxide to err. on the safe side, if inexperienced in water chemistry and fish.


For a man who knows so much about the chemistry of both aquaculture and agriculture, I'm really surprised you don't think the two work together.

[Crusty]

For a man who knows so much about the chemistry of both aquaculture and agriculture, I'm really surprised you don't think the two work together.

I am not sure where I mentioned they do not work together? In soil they work fine no doubt in that, just not in water with fish. There are alternatives to using hydrated lime as a buffer, especially for the inexperienced, that does not have any risk to the fish at all. So why use one that does? The OP asked what and how much. The what was suggested and I simply suggested an alternative source of calcium. The how much was not answered, but really it depends on the plant and the pH of the soil/water so testing would be required to know how much.

There is no requirement that you believe what I say or suggest I could care less. Have at it, throw some hydrated lime in with your fish, it really is not my issue.

[Outbackozzie]

Calcium Carbonate will work, a lot of people use Potassium Carbonate for the changing of PH, and the addition of Potassium also. 2 for 1 :)

[Murray]

The two I recommend,ie, hydrated lime and "Eco Rose" are recommended because they are very easily obtained. It is not wise to use them together. I use them alternately about 3 weeks apart.

We are talking very small amounts by the way, Aquaponic sytems tend not to have the pH swings that other types of systems do. In fact it has been my experience that the "drift down" in pH actually takes place over several months, the need to intervene by buffering with the two elements mentioned is not all that often, and by no means drastic.
I have stocking bags of crushed egg shells in my systems and that does a fair job although it is not a complete answer.

[darashee]

Ok, I understand a fair bot about aquaculture as I study it at TAFE ~ we just don't cover aquaponics ~ therefore this part is new.

With the addition of planting trays into my system, a NTF system was designed with a large biofilter. (total of around 1000L)

what I am interested in, is knowing where I can obtain further info on these nutrients, and where I can buy them from.

Obviously Seasol isn't a problem, and I see that it has a lot of trace elements needed, I guess I wonder how much, how often people use it.

The calcium and potassium, Murray you said egg shells partially work? Would you mind elaborating, and advising how you over come?

i am still a touch confused by the term 'buffer' doesn't it mean preventing the pH from raising or dropping? is the hydrated lime and eco rose designed to get it back to the correct pH level, or do they do other things?

Also, has anyone used zeolite?

[aussieap]

Hi.
Firstly, the UVI model uses calcium hydroxide and potassium hydroxide as pH buffers. They add them to the sump, so there is no chance of 'hot' zones in the fishtank burning fish gills. If it's been good enough for them for 30 years, it's good enough for me.

Potassium, phosphorous and chelated iron are the only additives in the UVI model. You get the beneficial effect of the rise in pH with the first 2 AND they add required nutrients . This is neat bc those 2 elements can be deficient in fish food and hence ap systems. Fishfood is likewise low in iron so we add that in small amounts.

Are you sure it is the nitrite at 20 and not the nitrate? I think u mean nitrate. If nitrite do not add fish til this drops to zero.

Just keep an eye on ur plants and test ur pH regularly, each few days at the start. Your plants will tell u if they are lacking in something and keeping ur pH around 7 will keep the fish, plants and nitrifying bacteria pretty happy.

Hope this helps.

[Murray]

Hydrated lime and Eco Rose are to be found in hardware stores.
As stated earlier in another post, these two items are not, strictly speaking, the exact chemicals needed, but they are close enough and easily obtained for very little cost, and they do the job.
If we were running a large Aquaponics farm then we would be a bit more scientific , but for the home system it will work well.
Aquaponics systems, when working as they should, drift down in pH over time and the pH needs to be brought back up to as close to 7 as possible, or better still using very small, but more frequent applications is kept at 7.

[fishfood]

Yes Murray i agree on ph mine drifted to 5.5 inoticed the plants not doing as well so i added a lot of shellgrit and some calciam carbonate to one if the empty grow beds last time i checked the ph was over 6 and stuff is booming

[Crusty]

Hi.
Firstly, the UVI model uses calcium hydroxide and potassium hydroxide as pH buffers. They add them to the sump, so there is no chance of 'hot' zones in the fishtank burning fish gills. If it's been good enough for them for 30 years, it's good enough for me.

Potassium, phosphorous and chelated iron are the only additives in the UVI model. You get the beneficial effect of the rise in pH with the first 2 AND they add required nutrients . This is neat bc those 2 elements can be deficient in fish food and hence ap systems. Fishfood is likewise low in iron so we add that in small amounts. <----->.

Personally I use both sodium bicarb for pH buffer and calcium chloride for hardness. However, I would not suggest chloride if you do not know how to handle it. I am keeping in mind that many people are not operating a UVI system and do not have a sump, thereby they will need to add the calcium hydroxide to the growbed, which simply drains into the fish. Perhaps it has had time to settle and perhaps not. I would not use it myself in that scenario.

I am very interested to know what form of Potassium and phosphorous you are using.

[Murray]

Hi Crusty,
Phosphorous does not normally need to be added to an Aquaponics system, also Sodium Bi carb is not used as a buffer in Aquaponics systems as over time the resultant increase in sodium is not desirable.

[Outbackozzie]

Obviously Seasol isn't a problem, and I see that it has a lot of trace elements needed, I guess I wonder how much, how often people use it.

The calcium and potassium, Murray you said egg shells partially work? Would you mind elaborating, and advising how you over come?


Seasol, 1 cup (250ml) per 1000l of system water initially. 1/2 cup per month or so thereafter, unless you notice things not setting fruit well. The potassium in seasol helps with fruiting and tuber plants also (potato etc).

Calcium in the form of seashells or eggshells breaks down over time to prevent the ph drifting too low.

I have about 2kg of shells buried throughout my 8kl system, and ph stays at 7.5 all the time. Hasnt changed in over a year now.

[darashee]

So, if I add the seasol mentioned ~ do I still need to add potash?? if so, how much per 1000L

[Outbackozzie]

Depends how severe you potassium deficiency is....I have had a bag of potash sitting in the shed for a year now, never had to use it yet.