Algae Diet.

[Dave Spencer]

Hi Tom,

I have been trawling around a bit on the internet, but have found it hard to pin down the list of algaes`nutritional requirements. Light, nitrogen, phosphorous......fair enough, but what about micros such as boron, iron, molybdenum etc.. Is the list the same as aquatic plants, but maybe with a variation on importance, or are there nutrients not in the plant list, or vice versa?

Cheers, Dave.

 

[Tom Barr]

Some plants and algae have wide variations, but pretty much most things need the same stuff for basic nutrients.

A few have various special needs, but these are the exceptions, not the rule.

Regards,
Tom Barr

 

[Dave Spencer]

Cheers Tom,

I ask because I am constantly reading people giving advice to limit nitrates or phosphates to combat algae. I just wonder why it is these two particular sources of nutrients that keep getting targetted in the cause of, and fight against algae.

If excessive amounts of nitrate and phosphate cause algae, then why not excessive Boron or Molybdenum?

So if what people are saying is true, exactly at what level do nitrates and phosphates trigger algae. Following on from this, exactly what levels do they need to be reduced to defeat algae. Unless these people are using 100% RO water, I don`t see how they can get the figures down to zero.

I have had three algae outbreaks in recent months. One was due to a major rescape resulting in spirogyra. I dare say the reduction in plant mass and disturbing the substrate and releasing ammonia caused this. The other two have been caused low, fluctuating CO2 and an instance where a CO2 bottle ran out without me noticing, resulting in rhizoclonium and cladophora.

I add EI ferts to two high light tanks and a reduced amount to a medium light tank and have never induced an algae outbreak in this way.

Why is it always nitrates or phosphates they blame?

Cheers, Dave.

 

[Tom Barr]

Dave you have good points, the same I asked myself.

The other thigns you can add to such a list are light and CO2, yes, limiting algae via light.

You do not limit it really, just slow it's growth with all of these limitation methods.

The thing is, you never really limit algae if you keep macros or plants, they need more PO4 in every case. 20ppb for algae and about 50ppb for submersed plants are the limiting ranges.

As far as NO3, most every species of FW algae is very much able to grow at 0.2ppm of NO3 rapidly.

How are you planning on keeping the range of NO3 at that or lower as well as stable?

Know of any way to measure PO4 accurately between 20 and 50 parts per Billion?

One reason B and Mo are not targeted because they are rarely limiting in natural systems and they are merely traces. So the plants or algae do no need much and they are akso much harder to test for.

Ever seen a Mo or B test kit in the hobby?

I've seen algae in these natural systems with these super low levels.
I've also tried to induce algae at ery high levels using PO4 and NO3.

Never been able to do so without going above 10ppm of PO4 and 160ppm for NO3 so far. That leads me to conclude in FW planted tanks, these cannot be limiting growth of algae in the presence of plants that are taken good care of.

Your experineces are very common and so are your thoughts with agae.
If you had done a large water change after that large rework/rescape, algae likely would not have crept in, likewise after big trims, doing more feequent water changes, havign over sized filters, lots of flow etc helps.

As you have seen, more light can make the system LESS stable.

Never forget that interaction with more light.
You have a lot more wiggle room with moderate to low light.
Green water is proportionally harder to induce with NH4 with less light.
So the amount required of /NH4 to induce GW is different depending on the amount of light and the amount of CO2.

While plants are limited by CO2 most of the time in non CO2 planted tanks, this same issue also limits algae. Adding less light + low limiting CO2 can really limit algae growth, just as it does limit plant growth.

If there is very little NH4 in any system left over for algae, due to stable conditions, stable water changes/export etc, then you end up with little algae.

I've been hearing that excess NO3 and PO4 cause algae for 30 years. I have my doubts in natural systems that have plants. You add these nutrients and end up with more weeds, not algae. There's a lot of strong specific research that supports this also.

There is no specific strong research that support the view that excess NO3/PO4 causes algae. Not in our tanks, not in natural planted lakes etc nor rivers. Comparing rivers and lakes without any plants and high biomass is hardly a fair comparison.

But if no weeds are there, then yes, you may get more algae if those are limiting nutrients in the natural system.Something is going to grow there if you add water and light, you have a choice of what that is.

Just ask these folks to prove that NO3 and PO4 cause algae in a fully planted tank.

Show what the limiting ranges for algae are, then show what the limiting ranges for plants are.

Then show that adding excess levels induce algae and be specific about what algae is induced.

Now if you accept that excess NO3 or PO4 induces algae and is the cause, not mere correlation, then we should be able to induce algae in all cases right?

If we cannot, then we must reject the hypothesis.

If you test on a fully planted well run tank without algae, then add lots of NO3 and watch, no algae.

Repeat with PO4.

Also, trying this with high light and rich CO2 shows the same patterns, we should see more of a chance when we add more, yet that too fails.

So I have little choice but to reject such dogmatic myths.
It's not that I love to argue or hassle, stir things up, it's just I know it's not true.

These folks don't.
They have algae, cannot induce it specifically, cannot set up a control tank that's healthy and well run, stable etc.

So all they have really is some correlation, a lot of speculation, no background research support, test only what they assume to be the causes and try to argue that those support their contentions.

That's a very weak position to argue from, basically all they have is a lot of belief and not any proof or evdience for support.



Regards,
Tom Barr