I am wanting to solicit opinions about what kind of water to use in an aquaponics system and also how to go about getting that water. Also, it seems that I have to fill the water back up an awful lot, is that normal?
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Murray Hallam adds a teaspoon of chelated iron into his siphons once a month. He says that should take care of iron deficiencies in plants. He also suggests adding trace minerals but says that isn't as important. The chelated iron, available at garden shops and online (I got mine from Amazon) doesn't harm the fish at all. However, the pH can't be high or it won't work.
Rick, unfortunately all that does is add to the list of aquaculture sources that suggest the 0.3 to 0.5 ppm range. I suspect that most of them will give that same answer.
If we ask the plant people, (also PhD types) we will always get an answer of about 2ppm to stave off plant deficiencies. (Which people, Universities, commercial AP types do with no apparent harm to the fish, at least not any that is noticable by the time they harvest them).
And the circle of questions/wondering begins anew...
Iron doesn't have to be added to AP systems regularly at all...
If your pH is high, then Iron will be one of the first trace elements locked out... and the first "deficiency" that will appear...
The addition of Iron will correct deficiencies quickly.... and is only needed in very small doses...
Maxicrop, will also provide Iron... indeed there is a "Maxicrop + Iron" product available....
However, it is not correct to say.... "the pH can't be high or it won't work.".... the very reason for the addition of "chelated" iron... is that the chelation process... makes the Iron available in pH ranges where otherwise it would not be uptaken....
Seaweed extracts, such as Maxicrop contain naturally "chelated" minerals... which is why it is beneficial...
Ultimately, unless the pH issue is addressed, or falls naturally with system age.... then not only will Iron continue to be a deficincy problem.... but other minerals as well...
Rupe, could you shed some light on the "Iron and what it means to the fish" questions a few posts back? Your input would obviously be much appreciated
but chelated iron is already 'bound" to another molecule and is less accessible than free iron. What we're dealing with is free iron dissolved in well water. I suppose oxidizing it with water is a form of chelation, but it doesn't really answer the question about safe levels of free iron in water for fish.
I thought that the binding to a chelating compound made it more accessible (and water soluable)? Actually it would seem the iron rich ground water (Fe2+) when oxidized into Fe3+ is more like anti-chelation...larger molecules, less 'soluable', able to precipitate into larger particles blablabla...
Either way though, your right it doesn't really help us out in answering the question of iron and fish safety. Maybe because the chelated iron is more 'accessible' (plant wise) and so soluble (small molecules) that it doesn't cause the physiological damage due to accumulation on the gills??? I highly doubt that that's the case, but don't really know... Again, just more conjecture. Maybe we could ask someone like Rupert, or Kellen Weissebach, or Nate Story directly if no-one chimes in or we get sick of trying to figure it out ourselves ...
Though, I understand that this is much more of a serious and immediate concern for you, with your source water and all...
I think the issue here is that Rick is dealing with an overly rich in iron Tap water that could be dangerous to fish if not dealt with somehow.
Most everyone else has been talking about the "normal" aquaponics problem with hard tap water and needing to add chelated iron to deal with the Iron lockout deficiencies experienced by plants.
Right. My question is still...(I might be missing something and having "one of those moments" but) how/why is it that almost all aquaculture source information says to keep the iron in the water between 0.3 and/or 0.5ppm, yet on the plant side of things dictates (under "normal" non-lockout pH ranges) that 2ppm is (generally) needed to not experience plant deficiencies.
It stands to reason that if you have adequate iron in your system (2-3-4-5 whatever ppm) but it's unavailable because your pH is high (causing lock-out) you will add even more iron in the form of chelates to alleviate the plant deficiency. Why does this not then 'hurt' the fish (more-so)? You would be well over the recommended 0.3-0.5ppm for fish.
And how is it that people like UVI are dosing iron every 3 weeks to 2ppm which is 7 to 4 times the amount given as safe by the aquaculture side? That is all I'm wondering. (And many, many other people, with no apparent harm to the fish.
Rick's water is 1.34ppm. Is this a problem for fish?.......... Somehow we don't know? Or, think that it is.
UVI's water is 2 to 3ppm. Is this a problem for the fish? ....Somehow we don't think so?
The above seems strange to me...
At a constant 2 to 3ppm Iron level, why could we not say 'UVI is dealing with overly rich iron in their water that could be dangerous to fish if not dealt with somehow'?
I'm really not tryin to be funny or anything, just trying to understand this clearly.
We know there's a healthy balance because in nature fish and plants survive very well; but is it ever perfect? I think there might be a difference between "ideal" and "real." If there's a concern for too much iron (or too much of anything), start low and observe. If the plants are happy and producing well, there would be no need to increase levels.
Well if UVI is dosing up to 2 ppm I expect that the level drops between doses so it is probably not a constant 2 ppm and their source water is probably not adding iron every time they top up.
With Ricks source water, he might want to get a test kit or something so he can monitor if his iron level in his system is building up over time or not and to start with when he fills up the system he might want to follow the advise of trying to precipitate and oxidize some of it so he is not too heavily loaded on the iron to begin with and then observe how the plants and fish do to decide how much he needs to worry about removing iron from his source water and how much the plants will use it up. They also make filters you can use to remove excess amounts of metals from top up water. Remember that fish feeds also contain some iron and other trace metals. Some people never need to add iron to their systems because their pH is in a good range and their fish feed/source water has enough. Other situations probably require removing iron from the source water.
I would also be curious to know if there is a difference on how iron affects the fish depending on what form it is in. I expect the non chelated form that tends to precipitate out may tend to be more harmful especially if fish gills happen to be a handy place where it precipitates thus causing the problems.
I'd never thought about the feed adding to the minerals, but that makes perfect sense. I tried chelated iron once and it had no effect, other than to turn the water a pretty color. But that was before our PH was under control. It sounds like quite a challenge to decrease iron, but options are available. It will be very interesting to hear what Rick's ultimate solution will be.
I think those are some very wise suggestions for Rick. Monitoring, using rainwater top-ups, and/or removing or filtering the oxidized Fe3+ precipitates (since they're not plant usable anyways), and observation.
Rick is in a real live situation with all that iron, and needs some smart, practical advice while I am just more or less wondering whats up with 'those' plant/fish numbers in a half-assed academic sense.
At any rate, there's no denying that his source water is quite high in Fe and he'll likely need to take some sort of corrective action(s) to keep that from accumulating.
If I remember correctly ferrous iron is generally given a lower "safe" value, particularly for fry...
This might be useful (not just for iron) for anyone trying to make heads or tales of their water analysis report...in a general sort of way...http://www.uaex.edu/Other_Areas/publications/PDF/FSA-9090.pdf
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