Still withholding PO4 but got another bump up. Again, all orthophosphate in the system now is autochthonous. There are a lot of active fish and they are not wanting for anything. This AM I broadcast sinking food consisting of shrimp pellets, Bug Bites granular and pleco sticks, and algae wafers. This I do twice a week. The automatic flake dispensers are timed for one event at 09:00 and one event at 18:00 every day. This is Tetra Color Tropical Crisps. Fresh frozen brine shrimp and blood worms soaked in Boyd's VitaChem goes in every other day, but sometimes two or three days in a row. There is no overfeeding in the sense that food is not being consumed, although I am certain that some small fraction of sinking items goes to the heterotrophic bacteria directly. Anyway, this is the source of PO4, as no supplement is being dosed.
K: Increase K2SO4 from 90 sec to 100 sec
Buffer: Increase KHBOOST from 110 sec to 115 sec
The change in NO3 is drastic. I double-checked the NO3 with another kit. Both the NO3 and the PO4 are down. Still withholding supplemental PO4; dosing of NO3 remains at 5 seconds. Since I began making a point of noticing, this is the second time NO3 has dropped in this way. The second day after a generous feeding with fresh-frozen and sinking, the NO3 drops about 3 ppm. All the heterotrophs, bacterial and animal, process protein fairly quickly. Taking the data at face value, foraging by consumers > deamination > ammonification > nitrification > assimilation by producers is a two day "cycle" in this ecosystem. Thus far, it is clear that autochthonous orthophosphate is sufficient, or very nearly so, for the P requirement of the entire plant community, provided that a minimal level of animal metabolism is occurring on an ongoing basis. I am inclined to say that the same can be said of autochthonous dissolved inorganic nitrogen (DIN), almost entirely NO3 at any one time due to practically instantaneous nitrification. The variations suggest that the plants consume phosphorus and nitrogen rapidly, the daily changes being made obvious by deliberately holding their peak values within oligotrophy. A 3 ppm fluctuation is small where NO3 at, say, 12 ppm is normal, but is large where 5 ppm is a target maximum. This, of course, is being accomplished with the streaming water change regime. Without the constant turnover, the feeding of the fish at the present generosity would cause the system to lapse into mesotrophy. A small source of allochthonous NO3 assures a minimal level.
The 5 second dose is experimental. With this, along with the flake feeders, I have not seen NO3 go below 1.5 ppm. When feeding is generous, the NO3 goes into 4 - 5 ppm range. Fluctuations seem to be related to luxury feeding. I have not seen NO3 go out of control since beginning the streaming regime which has enabled my giving large quantities of highly nutritious goodies to the fish. The plants show no sign of any nutrient deficiencies. The occasional day or two when the DIN is low does not slow them down.
I am dosing calcium as Ca(NO3)2, which means the Ca supplementation is tied to the NO3 supplementation. The current NO3 mix is part KNO3, part Ca(NO3)2. The Ca level is starting to fall off. I am modifying the mix to increase the Ca part. I may yet have to increase the NO3 dose rate just a bit. I would like to maintain the GH at 3 degrees with the Ca:Mg ratio at around 2:1. I have seen strange things happen with the earth-alkalis in this aquarium, from unexplained Ca increases to, more recently, unexplained Mg decreases. By "unexplained" I mean oddly inconsistent with the dosing, and too anomalous to be attributed to testing error. I have more to learn here, but I expect the streaming to help me tweak this into line.
Today I fed the normal amount of sinking food, but no fresh frozen. I will be interested in what is revealed in the testing.
Emboldened by the total lack of algae and the increasing shadiness from the growing Echinodorus, I stepped up daylight from 60% of max to 70%. I can barely see it, but it will accelerate carbon fixation. Will I detect an increase in nutrient utilization?
Still withholding PO4. Dosing NO3 at 5 seconds. These parameters do (or at least, at the moment, appear to) correlate with the feeding, as discussed in the immediately preceding post.
I added a little CaCl2 directly. Five tspn Ca(NO3)2 were added to the NO3 vat. This is experimentation by trial - gradual dose and test. When I like the way calcium is being managed I will have to measure the concentration in the vat so I can pin down the mix.
Yesterday PO4 was still just over 2.5 ppm. In light of Monday's generous feeding this was expected. I allowed the AM flake feeding yesterday, then shut off food. The PO4 is now declining. I will add no fish food until tomorrow (Thursday).
I will now state with certainty that at the present stocking population (total consumer bio-load), and with the current liberal feeding practices, an orthophosphate concentration circa 1.0 - 1.5 ppm can be maintained entirely by autochthonous nutrient development. No supplementation with inorganic solution (allochthonous source) is required to satisfy the phosphorus requirements of all macrophytes in the ecosystem. It is likely, in fact, that generous feeding of the fish can occasionally generate orthophosphate in excess of that quantity that defines strict oligotrophy, even in a densely planted ecosystem characterized by accelerated carbon fixation. There is no indication from observation of the jungle's growth, color, and general health that PO4 is deficient in a system which is deliberately maintained within oligotrophy. The ongoing strategy will be to promote the current general level of orthophosphate concentration, accepting the natural fluctuations of nutrient load developed by the animal community. The KH2PO4 solution dosing is discontinued.
The extent to which fish feeding will satisfy the nitrogen requirements of all the macrophytes is still an open question. As defined by oligotrophy, autochthonous NO3, being the greatest part of all DIN in the aerobic environment, should be 5 ppm maximum. Some lesser sustained value may be perfectly adequate for fertilizing the jungle. Since supplementary NO3 dosing is being done daily, it appears thus far that the plants are using NO3 faster than it is being evolved by autochthonous nutrient development alone. The NO3 level is highly variable, but has not exceeded 5 ppm except where supplement dosing has caused it to be. At the current rate of carbon fixation in this ecosystem, NO3 tends to decline without the allochthonous source. While fish food supplies a large fraction of the jungle's total nitrogen requirement, it may not be wholly sufficient. What I would like to know is whether this densely planted tank would be happy long-term with NO3 testing at 3 ppm - or even less. This is a dynamic situation. Measuring a value for NO3 concentration in the water column while the plants are feeding constantly - taking their requirement as needed without limit - is really only indicating that there is measurable surplus of NO3 in the environment. The plants are not being starved as long as NO3 is non-zero. An actual value, even if small, assures non-limiting; 'just-in-time' fertilization wants a safety margin.
All of these observations are carried out on a system that is using a continuous water change protocol as specified in a previous discussion. A fairly large volume of RO/DI water replaces nutrient-loaded water constantly. So as much - or likely more - of the autochthonous product is flushed downstream as actually serves as plant food. The purpose of this scheme is to discharge autochthonous organic wastes which represent pollution composed of increasingly recalcitrant molecules - polyphenols, cresols, and so on, that result from heterotrophic processing, or any that satisfy algal auxotrophic requirements. This stuff comes under the heading of dissolved organic matter (DOM), or dissolved organic carbon (DOC). Water changes of sufficient size and/or frequency are a reliable means of being rid of it. The water change scheme I am using now is working very well. The outstanding water clarity, algae suppression, and 400 mV redox attest to its success. I have found myself surprised that at the current streaming rate so much of the phosphorus and nitrogen requirement of all these large thriving plants is being supplied without significant allochthonous input. I began with the assumption that regular doses of supplements of inorganic solutions would be necessary to fertilize a jungle ecosystem. It turns out, a populous community of active and well-fed fish gets the job done nicely. But a lot of fish food means a lot of organic waste, and the large DOM component of the autochthonous product must be eliminated as quickly as it develops or the system will not work properly.
After the extra manual supplementation done yesterday, I am a little surprised that the number for Fe today did not get a significant bump. I have done the same again. As a hedge against Fe deficiency, I put in 20 ml ferrous gluconate. This drove the ORP down to 247 uS/cm; ferrous gluconate is a reducer. Redox will return to its normal high as the plants use it up. It will be interesting to see how long it takes to recover.
Yesterday the only food was the AM flake. Still withholding NO3 and PO4. From Thursday's sinking and flake feast it is clear that the PO4 got a fast and durable bump and is now declining. NO3 got no such bump and is declining rapidly. What the data mean to me is that the ecosystem is metabolizing protein apace, and the plants are taking up nitrogen as fast as its usable forms evolve.
Today I am feeding fresh frozen while withholding NO3 and PO4. What kind of peaks will I get?
Since I have not been dosing Ca(NO3)2, no Ca at all has been dosed. Calcium is declining. Since the Mg dose was boosted, the total GH has been kept to about 3 degrees and the Ca:Mg ratio has moved from 3:1 prox to 2:1 prox. Without dosing Ca the balance will soon go akilter. If NO3 dosing resumes, so will Ca. Chasing the numbers this way seems unnecessarily complicated. I should dose CaCl2 separately and switch to all KNO3.
Iron is high from yesterday's big dose, as was expected. I will withhold Flourish until Fe drops below 0.2 ppm.
There are no significant changes in K, Ca, Mg, or KH.
The NO3 got a 2.5 ppm bump and the PO4 got a 1.1 ppm bump from yesterday's feeding. Today I fed extra flake and the usual amount of sinking food. Still withholding NO3 and PO4.
Orthophosphate regularly exceeds the specification limit for oligotrophy being sought. I am adding six ODEs to the schedule - 23:00, 00:00, 07:00, 11:00, 12:00, 19:00. All the dosing will need recalibrating.
Today I tested for chloramine at the carbon block output. I am ready to use more RO/DI.
A few thoughts about just what is being dosed in this aquarium.
High fish population with liberal feeding invites close inspection as the autochthonous source sufficient for plants. Already there is good evidence that, for an oligotrophic ecosystem, there is no need for allochthonous orthophosphate, and it is very possible that the need for allochthonous DIN may be reduced or even eliminated also. Here is a common conception that must be reexamined, that a densely planted tank will require routine fertilization, typically with KNO3 and KH2PO4. This is certainly the case in thinly populated tanks perhaps, but the extent to which the allochthonous sources are required is determined by the contribution of the inherent baseline autochthonous sources. For this heavily stocked oligotrophic aquarium, the need for "customary" dosing was a preconceived bias. I did not fully appreciate this fact until I began precision testing. As previously discussed, some NO3 supplementation may yet be needed, but the dose rate will be consistent with oligotrophy. It is required only that NO3 be non-zero and less than 5 ppm.
Potassium is the third macronutrient that is heavily dosed as a matter of course. It is absolutely vital for structural and metabolic function and is stored by plants in large reserves. Excess K is not toxic so there is no down-side that it be supplied in concentrations that permit 'luxury uptake'. It is my opinion that a densely planted tank should have a minimum 30 ppm to 40 ppm K. Any chlorosis that appears in the plants cannot then be attributed to K deficiency. Potassium is typically (standard practice in the hobby) dosed as sulfate. This is due to good water solubility and the fact that SO4 is a principle source of S which is a secondary nutrient. So when K2SO4 is being dosed in large quantities, SO4 is building well beyond minimal requirement concentration. I have not tested SO4 in the jungle lately, but the last time I did it was above 200 ppm. Once the plants take their S ration, the excess SO4 is essentially biologically inert. The bias to be questioned here is the use of K2SO4.
Let me jump to the issue of buffer dosing, then I will return to potassium. SeaChem Alkaline Buffer and Brightwell Florin Delta KH+, both of which I use interchangeably, are proprietary formulations involving carbonic acid salts and no phosphates. We are not told more than this, which is a state of awareness averse to my nature, as much as I trust both companies generally. Carbonate and/or bicarbonate anions are the key bases. Sodium and potassium are typically the cations of these salts for the sake of water solubility. Certainly we should prefer K, which is a macro, to Na, which is an important micro, but ought not be excessive. It's easy to get enough Na from Flourish Comprehensive alone, while we are on the lookout for sources of K which we want in luxury amounts. The jungle is a HL/HT system using CO2 injection. I go through a LOT of buffer. And I go through a lot of K too. Is K2CO3 a water soluble source of both? Yes, it is. How much buffering capacity can I get from target K dosing? Or, conversely, what K ppm can I get at target alkalinity (KH)? I intend to find out. This practice is not typically seen in the hobby because most situations are better satisfied when parameters and the means of controlling them are kept separate. But alternatives are possible.
Along these lines, consider the possibility of dosing Ca by slow dissolution of CaCO3, particularly the aragonite form, as in a reactor. This works in water acidified by carbonic acid, i.e. CO2 injected, and supplies both ++Ca and --CO3 buffer. The same applies to MgCO3. The means of automatic dosing of these would involve a low-flow internal filter connected to Apex. It is something I am willing to try. MgSO4, which is in use currently, is an acceptable source for ++Mg and remains a viable alternative. Calcium is more problematic. It is soluble as NO3, which I am using now but am trying to separate, and it is soluble as CaCl2. Chloride is an important micro and can be supplied fully by Flourish Comprehensive. As the sole vehicle for dosing Ca, the chloride would be present at the level of a secondary nutrient. This is likely uncharacteristic of natural waters and may be undesirable. Providing Ca in the KH buffer just seems more elegant. I try to keep KH between 7 and 8 degrees, but this parameter has some elasticity. Hitting targets for ++Ca, ++Mg, and +K and achieving acceptable alkalinity using --CO3 would be ideal. If there is a shortfall in the KH, I can add Alkaline Buffer.
There are no significant changes in GH. Potassium is down a little. Iron is down 0.15 ppm in 24 hours; one day more it will be back to normal. ORP has fully recovered.
This will be the first full day for the increased water changes. I am feeding fresh frozen and green-based sinking, as well as the usual twice daily flake. In just 24 hours, NO3 and PO4 have declined considerably. Neither is being added as supplement, and will continue to be withheld. Tomorrow's numbers will be interesting maybe?
Yesterday I put 200 ml (full dose for this tank) of Waste-Away heterotroph culture into the water. As always, they went to work in no time; the DO dropped to 6.8 ppm mid-afternoon. There was a lot of organic processing going on. I have been using this product for years. With the new regime I am implementing in this tank, I will be rolling regular dosing of Waste-Away into the schedule. I have an enormous mature bio-filtration system on this tank, and the biofilms no doubt include every aerobic bug known to the hobby and then some. So I don't think Waste-Away answers an absolutely critical need for my tank. The fact that a transient O2 consumption peak occurs when new heterotrophic culture invades the system is solid evidence of BOD. Waste-Away delivers a kick to the system, useful in a heavily stocked and liberally fed community in which the deliberate strategy is to evolve macronutrients for plants, a situation wherein BOD is necessarily high. In this sense, I find using Waste-Away to be necessary.
After yesterday's feeding, NO3 and PO4 got bumps just as expected, but they did not go out of bounds. I am feeding fresh frozen, green-based sinking, and twice daily flake again today. I expect similar bumps tomorrow from this, but am hopeful that the new streaming rate will restrain them.
Early days yet, but this preliminary result suggests that the sought after balance is being struck.
Iron fell only 0.05 ppm in the last 24 hours, so my prediction was off. If the plants wanted a few days of luxury micro this will do.
GH is down and it appears to be mostly Mg depleting. Potassium and buffer are also decreasing. The new streaming rate is having an effect already. I am about to implement the carbonate dosing experiment discussed in Monday's musings.
Friday, Saturday, and Sunday twice daily flake was restarted. Today NO3 is zero and PO4 is 0.61 ppm.
Saturday AM I did a 10% water change and started the MgCO3/CaCO3 reactor. I am using Brightwell NeoMag and CaribSea crushed shell substrate. Checking the GH frequently to guard against a runaway effect, there appears to be no reason for concern there. It's going to take time to bring the Ca and Mg concentrations back up. Meanwhile, I resume small daily doses of Ca(NO3)2 (10 seconds) and MgSO4 (40 seconds).
Sunday I withheld buffer and today started K2CO3. The mix is a cautious 50 g/L. I am adding 10 ml at a time, two doses this AM so far, and will continue until I get a perceptible increase in KH. I am continuing the K2SO4 for now.
Potassium is now 50 ppm and KH is over 8 degrees due to manual dosing of K2CO3 yesterday. Over half a liter of the 50 g/L mix was added to the tank throughout the day. I have adjusted the mix to 100 g/L. This now is the major part of the buffer solution and is being dispensed by the KHBOOST doser. The dose rate will start at 60 seconds (10 ml) three times a day. The dose rate for K2SO4 is now set for 5 seconds. The KHBOOST rate will establish 7 - 8 degree KH. If there is a K deficit with this, the K2SO4 daily dose will be increased. If there is a K surplus (over 40 ppm) KHBOOST will be modified by increasing the SeaChem Alkaline Buffer : K2CO3 ratio.
I ran the MgSO4 doser for about 30 seconds (5 ml) this AM to boost the GH. The water is extremely soft. I want to get the GH back to 3 degrees with Ca:Mg = 2:1. At the present water change rate I don't look for the CaCO3/MgCO3 reactor to achieve quick results.