Or at least that's the best title I could think of. Perhaps "Musings of an Aquatic Madman" would be more descriptive. You know you've become obsessed when you watch the Macy's Thanksgiving Day Parade, see the big Santa balloon, and blurt out "Santa's got dropsy!"
(I really did this.)
In the past I've been rather cavalier in my use of micros. Sometimes I've substituted Microplex for CSM+B on basis of iron content alone, ignoring all other differences. Many times I've probably added far more iron, or other micros, than is really necessary; assuming it to be harmless.
More recently my experiences have been that while deficiencies are to be avoided at all costs, it's also beneficial to limit excesses. My macro dosing has already undergone major changes to meet this philosophy, and I'm quite happy with the results. I figured it was time to give the micros the same treatment, even if the reward might be less, or even unnoticeable.
Micros are trickier, though. Most of us rely on a few commercial blends, sometimes with one or two key additions. Only the most hardcore planted tank enthusiasts go so far as to make their own micro blends entirely from individual ingredients for complete control. I'm not quite that hardcore! But I still had specific goals in mind, and I wanted to see if I could meet them without going to that extreme.
I'll preface this by saying that my goals may differ significantly from yours. That's fine. I invite you to keep reading if you desire to tweak your micros, as you may still find the example of how I achieved my goals useful to accomplishing a different set of goals.
1) I want a liquid micro solution, which is easier to dose into a wide variety of tank sizes. The solution should add 0.1ppm Fe per 5mL into a 10G high light/tech tank (you may consider this a light dosage, but keep in mind that I dose daily, as I find it easier to remember.)
2) I also want this solution to be usable in all my tanks, regardless of type. Dosage can simply be adjusted downwards for low light/tech tanks, but there is another issue to consider. In my low tech tanks, my tapwater's pH is high enough that the Fe EDTA in CSM+B quickly falls out of solution. In some cases, I've had to add triple the amount of CSM+B that would be EI dosed into a high light tank, to avoid visible iron deficiencies in a low light tank! Doing that, I worry a bit that all that iron - and other elements with lower toxic thresholds - are precipitating out and accumulating in the substrate. So instead I prefer to add extra Fe DTPA, which is more pH-stable.
3) But remember, I'm trying to both prevent deficiencies, and limit excesses. Iron in particular is under my scrutiny. I'm pretty satisfied with most aspects of CSM+B. But if I add more iron from Fe DTPA on top of CSM+B, then I get enough iron in low tech tanks, but a larger excess in high tech tanks. And if I reduce CSM+B to to prevent the latter, then I risk deficiency of other traces in all tank types. Well now, that's a conundrum, stuffed in an enigma, and wrapped in bacon. What I'd really like to do is take 50% of the Fe EDTA out of CSM+B and replace it with an equal amount of Fe DTPA, but that's impossible.
The Game Plan:
First off, I realized that CSM+B was a poor choice if I wanted to add Fe DTPA, yet limit iron. Microplex is lower in iron, so I suspected it might be a better trace mix to build on.
But it's also about 16X higher in copper. As I mentioned at the start, I have substituted Microplex for CSM+B on basis of iron content alone, meaning I dosed 16X more copper. Nothing bad happened, at least that I noticed. Of course, I don't keep shrimp, for which copper is more of a concern; yet even a few shrimp keepers have reported doing this substitution without issues. Let's assume for safety's sake that Microplex is near toxicity. Copper is reputed to have a narrow range between toxicity and deficiency. If that's true, then at 16X less CSM+B may actually be near deficiency! So a copper dosage somewhere between the two should be a good compromise. And so I add one more goal:
4) I want to limit tank copper levels to less than 0.15ppm, in an absolute worst-case scenario. With 0.15ppm being quoted a few places for treating algae and disease with copper, while still being relatively safe for plants and fish. And the worst-case scenario being that none of the copper dosed leaves the tank except by water change. Plant consumption is zero, or is equaled by copper contribution from fish food. In reality, copper levels will be lower, probably by quite a bit.
Achievement of Goals:
Time to crunch some numbers. But first a concise recap of all criteria:
I want to mix 1.875 cups (443mL) of a Microplex-based liquid micro solution, providing 0.1ppm Fe per 5mL into a 10G. It will be dosed daily, with a 50% weekly water change. At least 50% of the Fe must come from Fe DTPA. All other traces must roughly equal or moderately exceed the amount that would be provided by a reference solution providing the 100% of the Fe from CSM+B. Cu is an exception, it can exceed the reference by a large amount, but the worst-case Cu tank level of 0.15ppm must not be exceeded.
I'm using Yet Another Nutrient Calculator
, created by [Wet]. It's a great tool, and does most of what I need.
First, I told it to compute the amount of Microplex I'd need in my solution to reach 50% of my target of 0.1ppm Fe per dose in a 10G (remembering the other 50% will come from Fe DTPA). The result was 4.192g. But that also provides 0.02ppm of Cu per dose. Does this exceed our theoretical worst-case limit? For 50% water changes and assuming zero net consumption, there's a super-easy way to calculate what maximum tank levels will trend towards. Take the number of doses between water changes. Multiply by ppm per dose. Then multiply by two:
7 * 0.02 * 2 = 0.28ppm
Oops, we're over by just about double. Well, I can fix that by just cutting Microplex dosage in half, and 0.14ppm comes in right under the limit.
This means that only 25% of my desired iron is coming from Microplex. I can further increase the Fe DTPA to fix that, but I want to make sure I haven't cut other micros too much in the process. So I also had the calculator determine the ppm's for a reference solution where 100% of my target of 0.1ppm Fe per dose comes from CSM+B. How does Microplex compare in such a situation?
(Note that for generating these numbers, I increased my targets by tenfold, then divided the results by ten, to reduce rounding errors in the calculator. Otherwise I get silly results like 0.03ppm Fe, even when I specified a 0.025ppm target.)
Surprisingly good, despite such a relatively small amount of Microplex:
* Molybdenum (Mo) is equal.
* Manganese (Mn) is just a wee bit lower.
* Zinc (Zn) is 50% higher, but as it's reputed to have a fairly high toxic threshold, I'm not going to concern myself with this for now.
* Magnesium (Mg) is also about 50% higher, but still an insignificant amount compared to what comes from tapwater or GH Booster.
* Iron (Fe) is correctable with Fe DTPA, and copper (Cu) is within my limit; both as intended.
But look at boron (B). Microplex falls down here, providing 6X less than the reference. I've heard that boron and iron are possibly antagonistic, meaning raising one reduces the available amount of the other; so a 5:1 ratio of iron:boron should be maintained. CSM+B approximately uses this ratio. I also found a post referencing an article from Tom Barr, claiming that his article endorses this ratio; though as the actual article is behind a paywall I have not read it.
Well, I can add one more thing to my solution, without feeling I've gotten too hardcore. Especially when that addition is readily available in grocery stores as either borax or boric acid! Since it will be a small amount, I'm choosing borax (~11% boron by weight) instead of boric acid (~18% boron by weight), which results in a larger and easier to measure quantity.
Unfortunately, Wet's calculator doesn't include either substance. Gotta do this the old fashioned way, with a little help from Google's unit conversion:
1) Our 443mL of solution is intended to be dosed at 5mL per 10G. The whole bottle is therefore a single dose for a (443/5)*10=886G tank.
2) The whole bottle will raise the boron of a 886G tank by only 0.003ppm. We want it to raise it by total iron (0.1ppm) divided by five, or 0.1/5=0.02ppm. The difference is 0.02-0.003=0.017ppm.
3) One ppm is 1mG/L. Our 886G tank is 3,354L. So we need to add (3354*0.017)=57mg of boron to the bottle.
4) Borax is only ~11% boron by weight, so we actually need 57/0.11=518mg of borax.
---If you're using a gram scale, stop here; otherwise, continue to convert to volume---
5) Borax density is 1.73g/cm3, so we need 0.527/1.73=0.3cm3 of borax by volume.
6) 0.03cm3 is 0.06 teaspoon. 1/16 teaspoon, at 0.0625, is close enough.
And finally, I am happy with my micro mix.
Mostly just a warm fuzzy feeling that I'm doing the right thing for my plants. That I've finally given micros a little proper consideration. And a possibly interesting forum post for you.
I really expected no major real-world changes, and I was not disappointed. Going into week three of the new micro solution, things are still growing great as always. The plants don't seem to mind the reduced iron or increased copper.
There is one possible exception. My Limnophilia aromatica does seems to be growing fuller and faster. Right after noticing that, I saw an old forum post suggesting it likes extra zinc; and the new mix does provides 50% more. However, I'm not confident that the new mix is responsible. I'd have to do side-by-side controlled tests to convince myself of that, which I will probably never do.
Just One More Thing:
My new mix, by using Microplex, also addresses one small concern I've had with CSM+B. I'm stealing someone else's picture (but with credit) to show it, as their camera is far better than mine:
It's not very homogenous. Lots of distinct particles of different materials, with different particle sizes. I'm still on my original bag of CSM+B, nearly ten years old. At some point I noticed those different particle sizes started to separate out into differently colored layers. A good shake was required to mix it back up. But is that really enough to ensure consistent dosing?
Try looking for the copper. It's a good example to demonstrate my concern, since it's blue-green it's easy to visually isolate. You'll find relatively few particles of it. If you're dry dosing a tank with CSM+B, how many copper particles will you get in your small measuring spoon? One? Four? Zero? It will be different each time. Using a liquid solution helps, because since you're measuring out more CSM+B, variations will hopefully be averaged out. But it still wouldn't be completely consistent.
Now look at Microplex, picture from Green Leaf Aquariums:
At least visually, it's absolutely consistent. It will never separate or require shaking. Again, I get that warm fuzzy feeling using it; knowing I've eliminated another variable, even if it may be insignificant.
And with that I'm done. As I was filing the notes on this whole process away in my aquatic diary for future reference, I figured at least a few people might like to see them. So I wrote them up proper and posted. If you've made it this far, then you're probably one of the few, and I hope you find it useful.