aphanizomen flos-aque (heterocystous cyano) and microcystis aeruginosa (nonheterocystous cyano) both grow fastest with ammonia, nitrate, and then nitrite and atmospheric N2, in that order. most cyanobacterias follow the same pattern.
We only have one pest genus: Oscillitoria. They really are not heterocyst forming BGA's, but they might still fix N2 gas nonetheless. Phormidium I found in a few samples also, semi rare though and the tank was nasty.
the idea that cyano is caused by a lack of nitrates is like saying that humans are caused by a lack of sugar. not only can cyano use nitrates, the only better fertilizer for cyano is ammonia.
I do not think any said they cannot use NO3, we have stated that BGA is correlated with a reduced NO3 level(under 5ppm), to the point where it starts affecting plant growth(eg, limited N for plants). Limiting PO4 does not cause any algae bloom really(GSA mostly), so that was popular in the 1990's and not NO3 limiting.
This(lower NO3 below 5ppm(?) appears to induce Oscillitoria in planted tanks. There is no way to limit nutrients for BGA's in planted tanks, their demand for nutrients are minute compared to plants.
Indirectly, plant growth appears to suppress algae.
Perhaps when BGA's detect lower O2 in the root zone, or the vegetative cone, they will bloom and grow. Plants are not growing, it's a good time to grow. Otherwise, they just sit there. Mostly between the glass and gravel below the soil a little bit.
Once the NO3 drops, then they bloom.
i hope i am making sense here. for the longest time i have wondered at how people can adamantly disagree while observing two halves of the SAME phenomenon.
I do not think ANYONE has ever suggested that we are limiting BGA with nutrients.
because of cyanos unique properties, there are many valid methods of getting rid of it.
1: increase CO2 to boost plant growth. the goal is to strip the water of micro-nutrients that the cyano needs.
So you think that BGA are now micronutrient limited, whereas you argued above that they cannot be N limited? Leaching from plants provides ample supply, a few decayed leaves is all that is needed.
So what ppb of micro nutrients are limiting to Oscillitoria?
Any ideas? Estimations?
3: blackout: doesnt always work, but reduces the energy cyano gets from nitrogen fixation by about 90%. can kill it out right if oxygen levels get too low, which often happens underneath the mucilage sheath surrounding the cyano during prolonged darkness.
BGA does not get energy from N fixation, it's a energy expenditure(i think you meant to say this). Not that Oscillitoria even needs to fix N2 gas in any planted tank, there's always non limiting N in a planted tank for most any algae or BGA.
If not, we should easily be able to water change algae into submission for a few days before the plant reserves are depleted. Generally that leads to worse problems(again, back to poor plant growth as the root cause, not nutrient limitation of algae/BGA).
4 increase carbonates. this works by a couple ways. one, at higher ph phosphorus is more likely to coprecipitate out with carbonates, removing it from the water. two, many plants can use carbonates nearly as efficently as they can CO2. dispite injecting my tanks with a lot of CO2, i still see a big difference in shortly after water changes, or when i add more aragonite. plants grow, cyano starves.
I know of no submersed plant that has the same rate of growth at high KH as they do at high CO2. CO2 is greatly preferred in each and every case. It's an added allocation and energy expense to use HCO3 vs CO2.
I know of many aggressive weeds that use HCO3 as a carbon source indirectly, but it's still an energy expense in all cases.
I add lots of PO4, roughly 15 ppm a week from KH2PO4, my KH is low, about 20 ppm. BGA issues? I do not have any. I tend to care for my tanks well, however clients often are not consistent.
So when they stop dosing, I'll get call about algae, BGA etc.
CO2 tank ran out: green algae mostly. Low CO2= BBA
NO3 doser stopped= bga.
BGA is present in all my tanks, but it's regulated to the gravel below the surface on the glass nearest to a light source. It'll stay there for years, so it's not a question of having it inoculated or present, rather, is it a management issue?
No, not in the least.
We can rule out things like PO4, low KH, etc as direct factors.
I think you might be on to something with O2 however.
When plants are limited, mild moderate or strongly, then they reduce growth and also reduce O2 evolution from leaves(veg cones/apical meristems etc) and also roots. They do not release much O2 at night. Indirect growth reduction might be a trigger for many species of algae.
Bacterial links to the O2 levels might be a player also. No one really knows.
6 i use a focusable UV-C laser for this. works like a charm. it doesnt take much of an exposure, so using a germicidal bulb the same way you would if you were sanitizing vegetables is usually enough to make quite a difference on the cyano.
Well, that is a NEW one, lasers.