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434 Posts
Hello everyone
I have a 100 gal tank with 3 150 w, single ended metal halide bulbs with included UV protection, 4.200 k, 19 cm above water level, this are on for 12 hours daily (no additional glass for UV protection but the one offered by the lamp each self, whole fixture is enclosed in a wooden frame that blocks exposure of the room to UV).
In this tanks all ferts (Fe from EDTA currently, TE from flourish, KH2PO4 ,Ca(NO3)2, KH2SO4 are dosed with dosing pumps which keep the ferts at constant levels absolutely controllable ppm wise.
The substrate is pure fluorite with 1 cm peat mixed with mulm on the bottom of it. A 150 w Rena cable runs all along the first 1 cm bottom layer and it stays on 24 hours per day that keeps the substrate worm with the intension of transferring partial fertiliser to the bottom from the column through convention (possible acceleration of decaying of peat?). This tank has great fast growth of all plants including ones like macrandra, didiplis, eleocharis parvulus aromatica nasaea e.t.c. plant coverage is between medium to high. Measurements NO3, free Fe +2 - Fe+3, PO4 are done with a hanna colorimeter and K with a Hanna turbidometer so the readings are very precise. There is 2.500 lt circulation pump on it attached to a pair of lifeguard filters with 20 micron micro filters and a huge biological filter full of bioballs.
Sample testing values are:
NO3 7 ppm
Free Fe+3 FE+2 0,15 ppm
PO4 0,8 ppm
K 13 ppm
NO2 O
NH3 O
Kh 3
Mg to Ca ratio 1 to 20 (sudden high increase of Mg is triggering almost instantly new leaf curling in sensitive plants.
pH no current reading but there is ample CO2 almost 100 bpm all dissolved and plants bubble from hour one on light circle.
This tank has a constant problem of thread algae, BAG, Spot algae, algae seems to have a vigorous growth like the plants and needs to be cleaned daily to keep the plants "free" of it also the algae that settles down is removed daily with a siphon lately 10 % water changes (with RO currently to push the Gh and Kh down a bit) are done at the same time.
As far as I can observe all are in order. So some detective work is needed and I tell you after lots and lots of experimenting I am really frustrated. Increase of NO3 to 10 ppm or more (PO4 is always increased with NO3 in a ratio of 10 NO3 to 1 PO4) or a bit more will just increase the algae growth and at the same time the leaf size of all plants. Same goes for Iron the more I increase it the redder and more vigorous plant growth I get but also more algae (I can virtually nulify algae growth with a drastic decrease of Fe and I have tried this repeatedly but plants really suffer). The TE I keep stable dosing only 2,5 ml flourish daily.
Sensitive plants in the tanks to iron deficiency like parvulus and mayaca seem to excibit light green to white growth (Mayaca) also some curling is observed (from some effect of Fe to something according to my observations) when iron is reduced below or at 0,1 ppm, at 0,22 - 0,25 ppm of iron in the column all seem to be growing fine but algae increases really fast. I have tried both the iron gluconate and the iron EDTA. The approach with both irons is effective but still plants seem to be unable to cope with their iron demands in the amounts that algae will be kept at bay.
From my observations iron is probably the most catalytic fertiliser in growth behaviour in our plants.
But it seems that the amount of iron that is needed in the column with all this light to keep the plants happy (with no iron included in the substrate but only the fluorite, which I think is inert anyway), is a perfect algae inducer, grower as well.
From what I can read in Diana Walstad's book (one of the few people unfortunatelly for us that has done some serious experimenting):
So I was wondering has anyone observed similar problems or has some thoughts on the subject?
Sorry for the long post
Freemann
I have a 100 gal tank with 3 150 w, single ended metal halide bulbs with included UV protection, 4.200 k, 19 cm above water level, this are on for 12 hours daily (no additional glass for UV protection but the one offered by the lamp each self, whole fixture is enclosed in a wooden frame that blocks exposure of the room to UV).
In this tanks all ferts (Fe from EDTA currently, TE from flourish, KH2PO4 ,Ca(NO3)2, KH2SO4 are dosed with dosing pumps which keep the ferts at constant levels absolutely controllable ppm wise.
The substrate is pure fluorite with 1 cm peat mixed with mulm on the bottom of it. A 150 w Rena cable runs all along the first 1 cm bottom layer and it stays on 24 hours per day that keeps the substrate worm with the intension of transferring partial fertiliser to the bottom from the column through convention (possible acceleration of decaying of peat?). This tank has great fast growth of all plants including ones like macrandra, didiplis, eleocharis parvulus aromatica nasaea e.t.c. plant coverage is between medium to high. Measurements NO3, free Fe +2 - Fe+3, PO4 are done with a hanna colorimeter and K with a Hanna turbidometer so the readings are very precise. There is 2.500 lt circulation pump on it attached to a pair of lifeguard filters with 20 micron micro filters and a huge biological filter full of bioballs.
Sample testing values are:
NO3 7 ppm
Free Fe+3 FE+2 0,15 ppm
PO4 0,8 ppm
K 13 ppm
NO2 O
NH3 O
Kh 3
Mg to Ca ratio 1 to 20 (sudden high increase of Mg is triggering almost instantly new leaf curling in sensitive plants.
pH no current reading but there is ample CO2 almost 100 bpm all dissolved and plants bubble from hour one on light circle.
This tank has a constant problem of thread algae, BAG, Spot algae, algae seems to have a vigorous growth like the plants and needs to be cleaned daily to keep the plants "free" of it also the algae that settles down is removed daily with a siphon lately 10 % water changes (with RO currently to push the Gh and Kh down a bit) are done at the same time.
As far as I can observe all are in order. So some detective work is needed and I tell you after lots and lots of experimenting I am really frustrated. Increase of NO3 to 10 ppm or more (PO4 is always increased with NO3 in a ratio of 10 NO3 to 1 PO4) or a bit more will just increase the algae growth and at the same time the leaf size of all plants. Same goes for Iron the more I increase it the redder and more vigorous plant growth I get but also more algae (I can virtually nulify algae growth with a drastic decrease of Fe and I have tried this repeatedly but plants really suffer). The TE I keep stable dosing only 2,5 ml flourish daily.
Sensitive plants in the tanks to iron deficiency like parvulus and mayaca seem to excibit light green to white growth (Mayaca) also some curling is observed (from some effect of Fe to something according to my observations) when iron is reduced below or at 0,1 ppm, at 0,22 - 0,25 ppm of iron in the column all seem to be growing fine but algae increases really fast. I have tried both the iron gluconate and the iron EDTA. The approach with both irons is effective but still plants seem to be unable to cope with their iron demands in the amounts that algae will be kept at bay.
From my observations iron is probably the most catalytic fertiliser in growth behaviour in our plants.
But it seems that the amount of iron that is needed in the column with all this light to keep the plants happy (with no iron included in the substrate but only the fluorite, which I think is inert anyway), is a perfect algae inducer, grower as well.
From what I can read in Diana Walstad's book (one of the few people unfortunatelly for us that has done some serious experimenting):
Also is it a coincidence that the Dupla guys always used gravel mixed with lots of Laterite in their substrates?from pages 167 to 169 from The Ecology of the Planted Aquarium
Iron may be the limiting nutrient for algal growth in aquariums, if only because so many other nutrients (e.g., N and P) are so plentiful. Also, iron is the one nutrient that is required in fairly large quantities while being the least available in oxygenated water. Thus, I sometimes have problems with algae after setting up a tank with garden soil, because considerable iron is released into the water during the first two months (see page 131). Only after the soil has 'settled down', does the iron release stop and algal problems diminish.
a) Iron as the Limiting Nutrient for Algae
Iron's limited availability in oxygenated water sets iron apart from all other plant nutrients.3 This is because free iron (Fe2* and Fe3*), which is the only form that algae can use [28], doesn't ordinarily accumulate in the water. It either forms various iron precipitates (FeOOH, FeCO3, etc) or binds to dissolved organic carbon (DOC).
It is not surprising that most natural freshwaters contain only small amounts of iron, most of it bound to DOC. Indeed, the iron concentration of most oxygenated surface waters is less than 0.2 mg/1, and almost none is in the free form that algae (or plants) can use [26]. Hard water lakes, in particular, may have little available iron. Thus, one investigator [29] found algal growth to be limited by iron in several natural lakes. For example, phytoplankton cultures from Lake Ta-hoe (U.S.) were greatly stimulated by adding as little as 0.005 ppm Fe.
Enormous areas of open ocean have limited algal growth despite relatively high nitrate and phosphate levels. Because these areas are far removed from terrestrial sources of iron (e.g., soil dust), iron is present in exceedingly small amounts, less than 0.000056 ppm. Thus, when investigators added iron to experimental bottles containing these algae and their natural ocean water, algal growth was stimulated [30].
My point is that because iron doesn't stay around very long in oxygenated water, it can limit algal growth-in aquariums as well as oceans. Unlike phosphate and other plant nutrients, which can and often do accumulate in aquarium water, the reservoir of free iron in aquarium water is limited.
b) How Algae Gets Iron
Plants can get their iron from the substrate, but algae depend on free iron (Fe2* and Fe3*) in the water. Although iron in the water is indeed bound up, often to dissolved organic carbon, it is made transiently available by a common process called the 'photoreduction of iron'. The reaction for the photoreduction of DOC-bound iron is:
DOC-Fe3+ + light => Fe2+ + oxidized DOC
This light-requiring reaction, which also applies to manganese and copper, is greatly accelerated by DOC (my note: here DOC comes in the equation as well) [31,32,33]. The photoreduction of DOC-bound iron is invariably accompanied by the decomposition of DOC (see page 59).4 The Fe2+ released may be taken up by algae or quickly oxidized to Fe3+, which can also be taken up by algae or bind to fresh DOC, whereby the process repeats itself.
Different investigators demonstrated iron photoreduction using a variety of light sources ('Cool-white', 'Daylight', and Vita-Lite™ fluorescent bulbs as well as sunlight). However, UV and blue light induce the most photoreduction, because only wavelengths below about 500 nm are energetic enough to break the chemical bonds [31].5 Thus, investigators showed that only wavelengths below 520 nm released free iron from one DOC-chelated iron (Figure X-l). Algae grew well under normal light with chelated iron as the only iron source, but when light wavelengths below 520 nm (my note can that be a factor cause I do not use additional UV filter?) were filtered out, the same algae became iron deficient and would not grow.
Iron is bound to a variety of chemicals and different types of DOC. These iron complexes all have their own peculiar 'iron-binding tightness' and susceptibility to both photoreduction and chemical reduction [34], Thus, algae may, indeed, have access to some iron even in the dark. However, algae will get a far larger supply in the presence of light and DOC. Thus, Fe'~ levels in one lake were found to be almost 5 fold higher at midday when light intensity was greatest than at night [31] In natural systems (and aquariums) the photoreduction of DOC-bound iron is probably essential to supplying algae with iron.
Aquatic plants readily take up iron directly from the water [35], even when planted in iron-containing substrates [36,37]. For example, iron uptake by Hydrilla planted in a peat substrate was shown to actually equal iron precipitation as a means of removing iron from oxygenated water [36]. Plants would continuously drain free iron (Fe2+ and Fe3^) from aquarium water, thereby depriving algae of a much-needed nutrient.
In aquariums containing soil under layers, fertilization with chelated iron is almost surely unnecessary. Soils have enormous quantities of iron (see page 83). Not only do they contain plentiful iron, but also the anaerobic conditions that keep some iron in the free, unbound form that plants can use.
In my opinion, the substrate- not the water- is the primary place to provide plants with iron. Recommendations to maintain a certain water level of iron may be based on work that doesn't apply to the home aquarium. For example, aquatic botanists and hydroponic growers routinely add EDTA-chelated iron, but their plants may be sterilized beforehand or grown emergent. Under these circumstances, chelated iron is essential and won't promote algae. But what is appropriate for aquatic botanists and hydroponic growers is not always appropriate for the home aquarist. (my bold]
So I was wondering has anyone observed similar problems or has some thoughts on the subject?
Sorry for the long post
Freemann