Paul G

There is a "rule of limits" that states that if all conditions and nutrients are sufficient at one time for growth (or health, etc) of a plant, growth will stop, or the welfare of the plant may be impaired, if any one of these parameters becomes insufficient. All other things being equal, growth is limited by the parameter of least sufficiency.

The primary nutritional requirement is carbon. Carbon is the foundation of everything, structurally and metabolically. The plant acquires it from CO2 through the agency of light energy. We know that the lighting levels in our aquariums and the CO2 availability to the little ecosystems we create within are linked. Higher light intensity means faster growth, if there is an adequate supply of carbon, and lower light means slower growth with a greater certainty that the CO2 will be in good supply due to reduced demand. High light / high-tech systems are pretty much defined by the use of CO2 injection which is contrived to increase CO2 concentration. A major factor in the occurrence of nuisance algae is the imbalance of too much light for the quantity of carbon available. Algae want the light more than anything and are not limited severely by other factors. But I digress.

Plants need other stuff. In the process of fixing carbon the plant uses nitrogen, phosphorus, potassium, calcium, magnesium, iron, and a list of trace elements. Any one of these in short supply will adversely impact the plant, pretty much sooner than later in the case of the macronutrients. The whole idea behind getting plants to thrive is to assure they have all this stuff they need - obviously.

In the case of the high light / high-tech system, the carbon is elevated such that it cannot be a limiting factor, all the other nutritional requirements are dosed to concentrations such that none of them become limiting factors, and the light intensity is the throttle controlling the growth rate of the plants and the rate of oxygen production that results.

If I test for nitrate and get zero, I have two possible explanations. Either there is no nitrate being supplied, or nitrate is being supplied in such small quantities that the plants consume it all just before the moment I conduct the test. It might be just enough but there is no way to tell. But if I know that I am deliberately supplying nitrate, the zero result probably means I am running a deficit. If I supply enough nitrate that I get a non-zero result every time I test, I know for a fact that the plants are getting the nitrate and I am not running a deficit. The point of dosing nitrate is to bring about this state of certainty. There is no absolute numerical goal here. A repeatable test result showing 5 to 10 ppm simply proves sufficiency of concentration.

In an aquarium housing numerous or large hungry fish, the nitrogenous waste is elevated and nitrate will rapidly concentrate. Two most effective ways to alleviate this overage are organisms that eat it (plants and algae), or water changes (ugh!) that dilute it. So, if aquarium plants are your thing, here you have a ready-made nitrate generator. There may be no need to dose nitrate solution at all. If your nitrate keeps going up, just as you would expect in a fish only tank for instance, it means you haven't got enough plants in there!

That goes for phosphate as well.

I cannot stress enough the importance of dense planting. Lots and lots of hardy, competitive plants is the way to a healthy ecosystem. A high light system with CO2 laid on, while not obligatory, is the express route.
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What do you use to remineralize your Ro water?

I think SAE are unrated fish. Love the Cardinals as well. What other fauna?

Paul G

You will note in a previous post that I have a doser labelled GH BOOST (for General Hardness) which contains solutions of calcium, magnesium, and potassium sulfate. Ferric iron and manganese are also dosed in the MICRO/TRACE. These are the essential ingredients that characterize natural, biologically friendly water. Strictly speaking, calcium and magnesium are the earth-alkali ions that account for 'hardness' as it is understood by chemists, and the presence of these is what a GH test kit checks for. Calcium and magnesium are also what plant biologists call 'secondary macronutrients' and are taken in and used by the plants, so they are essential parts of the fertilizer program. I believe the correct ratio of Ca to Mg is between 2:1 and 3:1, with the calcium concentration in the aquarium water being as high as 30 ppm and the magnesium as high as 15 ppm. Tropical rainforest streams from which my fish come are typically soft water, so I aim to keep my GH as low as possible (4 to 5 degrees) while maintaining these values for Ca and Mg for the plants.

Also in this mix is potassium which is a macronutrient. I dose potassium (K) as potassium nitrate and as monopotassium phosphate in the N : 0 : K and 0 : P : K dosers, but also as potassium sulfate in the GH BOOST. Plants really eat up the K and there is nothing wrong with keeping it as high as 50 ppm.

These sulfate salts make up SeaChem's Equilibrium, which I would recommend if you aren't getting them in bulk and making your own dosing solutions. As a plant food it is not ideal but that is not its intended purpose. If you are dosing fertilizers as I am here, you would not need to use a remineralizer too. Avoid chlorides. Chloride is best regarded as a trace element requirement for plants. Calcium chloride may sometimes appear in a remineralizer product because its solubility exceeds that of calcium sulfate. Avoid sodium, also an important trace element, but not desirable in significant amounts. Equilibrium contains no sodium or chloride, nor should any respectable remineralizer - not if you're putting it into a softwater planted aquarium. One thing about Equilibrium - it cakes and sets up stone hard in the jar. Every time you want to use some, you have to go at it hammer and tongs, but that's just in its nature.

But, again, if you are getting into a serious fertilizing protocol for aquarium plants, you will NOT require a remineralizer prep for your RO water. I suggest you go to aquariumfertilizer.com and check out all the good info there. Also note how inexpensive this stuff is.

As for alkalinity, or carbonate hardness (KH), RO water has no buffering capacity, so that should be part of remineralization. SeaChem Alkaline Buffer is dosed in my KH BOOST. This is intended to keep the alkalinity at 7 to 8 degrees KH because I am using pressurized CO2; so when I push the pH down to 6.6 to 6.7, I know the CO2 in the water is between 30 to 40 ppm or thereabouts and that is the goal with the light I am using. A small amount of buffer is dosed daily to offset the acidification from nitrification. SeaChem Alkaline Buffer is a proprietary mix of salts. It works just fine.

Sulfur is a secondary macronutrient also, and it is supplied as sulfate in massive quantities. With all the sulfate that regularly goes into the water, it tests at over 200 ppm. There will never be a sulfur shortage; the excess is harmless.

A well-rounded micronutrient mix containing bioavailable iron will also have the important trace elements manganese, molybdenum, cobalt, zinc, copper, and boron. Nutritrace CSM+B is a popular mix and I use it. Aquariumfertilizer.com has it.
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Paul G

I keep the small South American tetras: Cardinal, Black Neon, Glowlight.
Corydoras, of which I have ten of various kinds.
I am a loach enthusiast, but I keep only species that do not get large. Just now I have nine of various kinds, two of which are seldom seen kuhliis.
Also present are some very shy Otocinclus, one reclusive whiptail loracariid, and a few glass catfishes.
I have just one Garra but will be getting a couple more soon. This fish is a very effective alga-eater.
There are ten (?) Cherry Barbs. We occasionally see little ones of these. Most of the adults in this tank were hatched and raised there.
The SAEs are an interesting contrast size-wise. The reputation of this fish as an alga-eater is controversial. They do pick along the leaves a bit, but there isn't much algae to begin with. I dispute the assertion that these fish will eradicate nuisance algae. They are just as fond of staple flake, brine shrimp, and blood worms as the other fish, and these items are the bulk of their diet.

Paul G

From hereon, I will use HLHT for high light / high-tech.

Today's numbers

NO3: 5 ppm
PO4: 3 ppm
K: 50 ppm
GH: 80 ppm (4.5 deg)
Ca: 60 ppm
Mg: 20 ppm
Ca:Mg = 3:1
KH: 108 ppm (6 deg)
pH: 6.65
CO2: 38 ppm
Fe: 0.18 ppm
EC: 720 uS/cm
ORP: 336 mV
O2: 9.7 ppm

The pH is the average of pH-R over the last 6 days. ORP and O2 values are average of the daily maximums for the last 6 days.
CO2 is usually stated on these statistics lists as a readout from the KH : pH chart, with middle values being interpolated. Today I performed a titration for CO2 and confirmed the number as spot on.

I will be trying to get the KH to trend up a bit to boost the CO2. I am happy with the pH being no lower than 6.6 and don't want to depress it further. I have concerns about the efficiency of nitrification below pH 6.8, that value already lying on the low end of the curve for autotrophic function (the main reason why I advocate large biofiltration capacity in HLHT systems). I am trying to get the light intensity up. A few days ago I upped the BMLs to 70% and I would like to go higher, but I'll need to make sure the CO2 is consistently coming in at 40 to 45 ppm. That means getting the KH well above 7 degrees. The higher light will crank up the oxygenation/oxidation processes which will in turn fortify the autotrophs. Everything is connected.

So, KH BOOST gets a bump up and the jungle goes into higher gear. I am expecting that, as a result of this, I'll have to bump up the NO3 again too.

The GH can go lower. At 4 degrees the earth-alkalis would be 72 ppm. If the Ca:Mg ratio is adjusted to 2:1, Ca would be 48 ppm and Mg would be 24 ppm. A close approximation to these numbers is my goal. I will add MgSO4 to the vat and reduce the dose from 20 to 15 seconds.

I am temporarily keeping the UV sterilizers turned off.
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Paul G

On Tuesday I again did some extensive pruning, including removal of most of the Ludwigia. I will be cleaning up large cuttings of this and replanting it. I also changed 22.5 gallons of the tank water. Regularly scheduled water changes are not part of the normal regimen. I think perhaps I do this on average about once every two months. It is a means of pushing the reset button and rebuilding parameters, which takes a few days. There is a definite "freshening" effect from a water change. I set up the surface skimmers for 24 hours and collected all the floating debris.

All the in-tank intake and return piping was disassembled and removed to a 2-hour strong bleach bath. These 1 inch pipes and fittings are the place where algae eventually show up, though not typically elsewhere in the tank. When I decide to take a day for major maintenance, the appearance of this piping factors heavily into that decision. I really should do this more often.

It has been 13 days since the screened intakes were swapped. So it seems I have to swap the intakes every 2 weeks, not every 3 weeks as previously stated.

Not especially happy that pH-L is consistently, and significantly, higher than pH-R, I have decided to install a CO2 diffusor in the left processing loop. This will be placed between the 40 watt sterilizer and the heaters. I will not increase the light until this is fixed.


Paul G

Today's numbers

NO3: 5 ppm
PO4: 3 ppm
K: 50 ppm
Fe: 0.27 ppm
GH: 76 ppm (4 deg)
Ca: 52 ppm
Mg: 24 ppm
KH: >8 degrees
pH: 6.7
ORP: 345 mV
EC: 950 uS/cm

Since the water change it was easy to bring the nutrient parameters back to normal. I am withholding GH BOOST just now and I will be interested to see how long it takes for GH to go to 3 degrees. At 3 degrees and Ca:Mg = 2:1, calcium will be 36 ppm and magnesium will be 18 ppm. When I hit these numbers, which I regard as ideal, I will completely reassess the dosing rate for GH BOOST. This is going to remain a softwater environment with non-limiting secondary macronutrient, so I will be watching the GH closely.

The buffering has been more difficult, and I am still in the process of adjusting it. Greater than 8 degrees gets to the CO2 dissolution goal.

Early this AM I installed the new CO2 diffusor. The pH-L meter is now giving appropriate responses. I will turn the BMLs up to 80%.

The UV sterilizers have remained OFF, and the iron values (and presumably other micro complexes) have been stable on an ongoing basis. I am now amending my philosophy regarding UV. It is a good thing to have the capability in the system in case it might be needed, but it does no harm to simply just leave it turned off. It is obvious to me that UV interferes with micronutrient/trace element provision to the plants, so to leave it turned on for no compelling reason can do a great deal of harm, or at least create uncertainty, in a planted aquarium. I dose the entire plant food/supplement protocol in the water column, so it all passes through the sterilizer vessels. It is counterproductive to deliberately decompose it. But, if I should ever need to implement UV sterilization all I need do is flip a switch.

I tested RO/DI output for chloramine. OK.