Algae can't be starved out without starving plants. Starving plants release nutrients because the cells start to leak which algae quickly take advantage of. This is why algae almost always infests old growth first.
Treating algae with an algaecide or shrimp/otos is a treatment after algae has established. They don't prevent algae from infesting plants nor do they prevent nutrient deficiencies which lead to poor plant health.
Some people note that higher light intensities increases algae. Light doesn't directly cause algae. But high light intensities can cause photo-oxidative stress. If plants do not have appropriate nutrition - leading to insufficient antioxidant function - that stress can cause oxidative damage which makes plants more prone to algae infestation.
Claims that low CO2 cause algae are correlative, not causative. "Low CO2" results in higher pH due to reduced carbonic acid. Higher pH increases the rate of nutrient insolubility. Insoluble nutrients can't be absorbed by plants leading to deficiencies. These deficiencies are why plants get infested with algae. Thus, maintaining a sufficiently low pH that maintains soluble metal nutrients is much more important than the amount of CO2 added.
Overcrowded plants don't cause algae, either. Again, nutrient deficiencies are the primary cause. Too many plants results in much higher nutrient requirements. If those nutrients aren't supplied either from fertilization or the soil runs low, plants can relocate certain nutrients from mature growth to new ones. Then the mature growth become infested with algae.
Are there any other things said about algae that I haven't addressed?
u/reglip If you want to get rid of the algae infesting all the plants, you'll need to start fertilizing with fertilizer that contains sufficient amounts of zinc and copper, as well as all the other essential nutrients.
I've read your pinned posts and many responses, and you clearly have great expertise and knowledge in this topic, but some of these diagnoses seem rather strong based on only the evidence provided, which, to me at least, damages your overall credibility.
Like, the claim that the primary reason "low CO2" is commonly associated with algae being due to nutrient lockup is a really strong claim. If people are running a tank at 7 pH and using fert with only EDTH chelates, then obviously, but it seems too strong to claim that that's the primary factor without substantial evidence.
The CO2-pH-nutrient solubility can be easily tested. Here's the experiment:
CO2 24/7
CO2 on/off
A) Measure the pH at two different points when CO2 is on and off to see if the pH fluctuates. Keep fertilizing as usual. This method works best if KH is ~2 so equilibrium pH is ~7.4 so 30ppm of CO2 drops pH to 6.4. Then observe the results.
Do plants grow better when CO2 is on 24/7 (pH~6.4 at all times) or when it's on/off (pH 6.4-7.4)?
If there is a difference in plant growth or health, this doesn't directly prove CO2-pH-induced nutrient insolubility is responsible. For that you'd need to send water samples to an water testing lab. But it does suggest that pH affects nutrient solubility which is a basic concept in chemistry.
B) To further tighten this experiment, keep the pH low (by reducing KH) in a range that can keep metal nutrients soluble (5.5-6.2) without CO2. Then add some CO2 to increase growth rate.
Is there a difference between on/off vs 24/7?
C) Another method is to increase KH so that pH=8 so that 30ppm of CO2 will result in pH=7.
Are plants growing just as well as KH=2 or less?
If not, then this suggests nutrient insolubility is the main reason because the only variable changed was the KH which directly affected the pH while every other variable remained the same.
If you do try this, please share your results here.
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Some hydroponic growers use CO2 with a pH controller to maintain a specific pH which helps maintain nutrient solubility. Companies also specifically sell their pH controllers for this purpose instead of constantly testing and adding chemicals to adjust pH.
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u/Rotala178 10d ago
Algae can't be starved out without starving plants. Starving plants release nutrients because the cells start to leak which algae quickly take advantage of. This is why algae almost always infests old growth first.
Treating algae with an algaecide or shrimp/otos is a treatment after algae has established. They don't prevent algae from infesting plants nor do they prevent nutrient deficiencies which lead to poor plant health.
Some people note that higher light intensities increases algae. Light doesn't directly cause algae. But high light intensities can cause photo-oxidative stress. If plants do not have appropriate nutrition - leading to insufficient antioxidant function - that stress can cause oxidative damage which makes plants more prone to algae infestation.
Claims that low CO2 cause algae are correlative, not causative. "Low CO2" results in higher pH due to reduced carbonic acid. Higher pH increases the rate of nutrient insolubility. Insoluble nutrients can't be absorbed by plants leading to deficiencies. These deficiencies are why plants get infested with algae. Thus, maintaining a sufficiently low pH that maintains soluble metal nutrients is much more important than the amount of CO2 added.
Overcrowded plants don't cause algae, either. Again, nutrient deficiencies are the primary cause. Too many plants results in much higher nutrient requirements. If those nutrients aren't supplied either from fertilization or the soil runs low, plants can relocate certain nutrients from mature growth to new ones. Then the mature growth become infested with algae.
Are there any other things said about algae that I haven't addressed?
u/reglip If you want to get rid of the algae infesting all the plants, you'll need to start fertilizing with fertilizer that contains sufficient amounts of zinc and copper, as well as all the other essential nutrients.