Technical fertilization questions

Blinky

Blinky

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I've been trying to find KNO3, and you guys were so helpful with that. I went to the hydroponics shop that was recommended, and they didn't have it. They had ammonium nitrate, calcium nitrate, and magnesium nitrate. I don't want to add ammonia to the aquarium, I don't want to add calcium in any significant quantity, but I realized I do add Magnesium in the form of MgSO4 so... maybe MgNO3 could substitute? I'd have the NO3 and just get the Mg from MgNO3 rather than the MgSO4.
I asked the man at the shop if he could tell me how much Mg I'd be adding to the water in relation to the amount of NO3, and he called the supplier - neither of them had a clue.
So I'm hoping that someone here can tell me if this is safe/wise to use or if getting the amount of NO3 the plants need will cause unsafe levels of Mg in the water. I've never seen a Mg test kit, so I'm not sure how I'd tell how much Mg's in the water. I've used MgSO4 at levels of 1tsp/5g before to medicate fish for constipation, so I'm hoping that MgNO3 wouldn't hurt the fish (however I'm not sure what effects high Mg would have on the plants, or if fish should be exposed long-term)
Anyone who can shed light on this, I'd really appreciate it.
 
Did you go to the Hydroponics store on Main and Gerrard (Jungle Hydroponics)? The one I recommended to you the other day SHOULD have the KNO3 (I went just last Friday, and they still had it)

It's sold in little plastic tubs and it's part of the "6 pack" that they sell for growing garden vegetables hydroponically.

As for using MgNO3, I would imagine it's possible, but you'd better ask someone else, as I'm not too proficient in this kinda stuff.

But just looking at it quickly, magnesium nitrate would be Mg(NO3)2, not MgNO3, so theoretically, it would add twice as much NO3. Mg(NO3)2 would have a molecular weight of 148 g/mol, so adding 1 gram of that stuff would give you 0.162 grams of Mg and 0.837 grams of NO3...or in terms of moles, 0.00675 moles of Mg and 0.011625 moles of NO3...Now if you were to dissolve that in 100 mL of water, you'd have 0.0675 M of Mg and 0.11625 M of NO3 in the solution.

That's pretty much as far as I would dare go, I'm not even sure if my calculations are correct, but it's a start :)
 
That's BIZARRE. I went to Jungle Hydroponics, the man was very helpful but not too sure of the products. He looked all over the store, and said they didn't have any. Hm. Maybe I'll wander back tomorrow and check it out again, if I'm in the neighborhood. Thanks again.

[edit] Darkblade48, I also wanted to ask you about the #6 trace elements mix from Jungle Hydroponics, since I think I saw you say you use it - I asked the guy about it, but his instructions were to use 'very little' which doesn't really tell me too much. So... I'm wondering if you can tell me exactly how you use it. I got a bottle and a dropper, since I figured I'd mix a batch and then dose when needed, but I'm not sure how much mix to use per gallon, or what the ratio of water:powder should be. These things need to come with instruction labels! [/edit]
 
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It seemed to me that this guy wasn't familiar with what I was asking for (I went in and asked for potassium nitrate straight off, since everywhere I spend time looking doesn't have any I just ask right away now). It's possible it's there and he just wasn't sure where to look - he was looking in the back of the store, and if it's where the trace mix was, he/we should have been looking in the middle of the store. Not his fault, and like I said he was extremely nice - he even called the company up to try and find out how much Mg there was in relation to NO3 in the Mg(NO3)2 (they couldn't answer him). I'm thinking I'll try the Mg(NO3)2 for now, unless someone says it's a bad idea, and get the KNO3 as soon as I can.

I mixed up a solution tonight and tested the levels. I put together what I had - anyone's comments are appreciated, I'm not ready to try it out until someone gives it the nod. I'm willing to not use this and go out and try to find the exact things in the PMDD formula if necessary, but I'm hoping I can come up with something that works, working with the chemicals I can find.

The mix:
- 4 tsp trace elements
- 6 tsp Mg(NO3)2 for N
- 2 tsp KCl (No-Salt) for K

There's no S in the mix anywhere, since I'm not using MgSO4 and there's none in the trace mix - not sure if that's a problem. I've got epsom salts I could add if that would help, but didn't want to add them to the mix since it would add to the level of Mg which may already higher than it needs to be. In the Krib's recipe their trace mix has Mg, and they use MgSO4 - since I'm not using either, I'm hoping the amount of Mg in my mix isn't too much, since they mentioned that too much will inhibit the use of other nutrients.

I tinkered with the levels and tested PO4, NO3 and Fe. 1ml of the above mix + 1 drop of Fleet gives me these levels in 1 gallon of (tap) water:

- 0.1ppm Fe
- 10ppm NO3
- 0.1ppm PO4

So now I'm confused (please forgive me, my last chem class was a long time ago and this is all new to me). If these are my target levels, and 1ml of the stock solution gives those levels in 1 gallon of water, won't I need a fair bit? I've been reading that it's best to add less than 1ml per day, but the levels would be minute - am I missing something?

[edit] I realized today that using the drops daily I would be maintaining the existing levels, not producing them from nothing, so now a small amount each day is starting to make sense... [/edit]
 
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I wouldn't be too sure on the effects of using Mg(NO3)2, so I'll leave that up to another (more experienced :)) member.

KNO3 is in the middle of the store, uhhh, about 3 metres away from the cash register. Somewhere in that vicinity.

Having no S may be a problem, but then that's why I used K2SO4 as well as KNO3 for my source of K. You could look into using K2SO4 instead of KCl, and it may work just as well. But of course, the point of PMDD is trying to add as little in terms of chemicals to your tank as possible.

You may or may not want the PO4 in the water, depending on how heavily stocked your tank is with fast growing plants, etc.

That mixture of the PMDD you made up seems reasonable. You didn't seem to mention it below, but from my calculations, it seems as if you mixed the 4 tsp trace mix, 6 tsp Mg(NO3)2 and the 2 tsp of KCl into 1000 mL of water.

Now let's say you have a 55 gallon tank. Adding 1 mL of the above solution would give you:

~ 0.1 ppm of NO3
~ 0.002 ppm of Fe

(Those numbers were just the same numbers you had divided by 55)
Anyways, the point is that if you were to dose something like 5 mL every other day, you'd be increasing your NO3 at a rate of 0.5 ppm and your Fe at 0.01 ppm. You may want to tinker with the amounts of trace/Mg(NO3)2 that you are adding, but then again, I'm not even too sure about using Mg(NO3)2.

Just my 2 cents, HTH.

By the way, what test kits are you using that can test Fe and PO4 within an accuracy of 0.1 ppm? Mine can only detect it in increments of 0.25 ppm
 
www.gregwatson.com will ship to you or anyonje provided they pay shipping etc.

KNO3 is fine.
KH2PO4 or Fleet etc
Traces

If you have a GH of about 5 or higher, you likely have plenty of SO4 and Ca and likely Mg as well. High GH(Ca and Mg) has little effect on aquatic plants.
Tap water has a lot of SO4 typically if there is is Ca and Mg. It's the anion balance most often in higher GH water.

You want a target of
1ppm PO4
10ppm of NO3 and you can simply forget about maintaining any meaningful Fe level.
Dose that like 3x a week at say 5mls per 20 gal etc.
This is a consistent type of routine and can be adjusted to find a good level for plants. Any adjustment should be observed for about 3 week's time.

It is critical to have the NO3/PO4/CO2/ in good shape while doing any test.
Othwerwise the other potential problems/changes might influence the test on the Traces.

You do not gain anything from low PO4/Fe as far algae, they are not limited in planted tanks.

If you doubt this, try to water change an algae problem away the next time.
You can use RO if you think the tap makes a difference.
I add 10-20x the PO4 you do and probably 2-6x the traces, I have no algae.

The focus should be on the plants' needs.

Regards,
Tom Barr
 
I have some KNO3 coming, I'm VERY happy about that - I'm still thoroughly confused but I'm sorting it out gradually ;)

Darkblade, I'm using Hagen Nutrafin kits. They're liquid reagents (Fe has a powder) and seem to work really well, though some of the tests can be hard to read because there's not much colour difference between levels. The NO3 kit reads 5, 10, 20, 50 and 110mg/L, the PO4 kit reads 0, .25, 0.5, 1.0, 2.5 and 5.0mg/L and the Fe kit reads free and chelated Fe depending on the reagent you use, and measures 0.1, 0.25, 0.5 and 1.0. I get them at PJ's Pet Centre in the Yorkdale mall, since Big Al's carries a NO3 kit I'm not too fond of (there's so much shaking involved!).

Thanks for the help guys, it's starting to make more sense. Everything I read seemed to talk about dosing 1ml or less, and I was trying to imagine how that would help at all! Knowing that it won't hurt to dose 5-10ml makes it clearer.

My tap water is ~3 degrees KH, so I'm guessing Mg wouldn't be too much of a problem. Like I said, the KNO3's on the way, but I do have this container of Mg(NO3)2 I can use as well.
 
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