OK....

Been doing a lot of reading on this forum and am confused by references to algae growing on some plants and not others. For example, Java Fern may get BBA before other plants due to low C02 and Java Fern's less substantial surface area and CO2 uptake ability.

Why would algae be more prone to grow on one plant as opposed to another assuming the general nutrient load is equally distributed throughout the tank? I thought allelopathy was bunk... is this not the case? My plants certainly don't mind growing next to each other.

If one plant is not growing as quickly as another (or is suffering) the only reason I can think of for algae to "choose" that plant is that it will actually feed off of a suffering/mal-nourished plant.

Thanks!

water flow maybe? if CO2 is low anyway, then somewhere out of the main flows will be getting far less exposure than somewhere inline with a powerhead. Just a thought.

I agree that the water flow may promote algae growth in some areas as opposed to others... But working under the assumption that the nutrients are evenly distributed throughout the tank how do we explain this? Or is it the case that given even distribution algae growth would be evenly distributed as well... But this does not seem to be the case.

because in areas of low water flow the exposure to co2 would be less.

Around every leaf of foliage on a plant there exists a thin barrier where most of the gas absorbtion takes place, if your lacking water flow across this area, then the plant is able to take up far less carbon than a plant that is in the main flow, as the CO2 saturation in that layer is less frequently replenished.

Im not saying this is definatly the answer, just that it could be

I think algae start growing preferentially on unhealthy leaves. In my tank I see much more BBA, when I have it, on older leaves that are not actively participating in the growth process - in other words, they are on the virge of dying. Once any algae gets started, higher CO2 concentrations are as welcome to the algae as to the plant, so I have had lots of BBA, again, on filter return pipes, on areas right in the flow from CO2 reactors, etc. The secret seems to be avoiding the algae ever getting started, and avoiding any unhealthy plants in the tank.

Hoppy,

Why do you think that you see the algae growth on the older/dying leaves? What is triggering the algae to grow in these areas?

I wonder if the actual process of the plant leaves dying is releasing nutrients (ammonia -> nitrogen) that the algae can take advantage of. I can't guess as to what in the actual growing process would inhibit algae growth. So... is plant growth inhibiting algae or is lack of growth promoting algae?

A faster growing stem plant easily avoids the BBA as the time factor for colonization is much shorter. Anubias have leaves that are exposed and long lived, so they have a lot more time to get colonized.

Actively growing plants give off O2, quite high in some cases.
BBA is not picky about where it grows but it will not grow on healthy plant tissue.
As far as BBA is concerned, that slow, virtually stagnant plant is a rock or piece of wood or glass etc.

BBA does not care, just as long as the leaves are not growing, stable and 1/2 dead.

The new spores settling also can tell if it's a healthy active growing plant, perhaps O2 levels, or the condition of the surface layer helps the BBA decide.
It would be bad for the BBA start growing on a fast growing stem plant and have it's likght blocked soon after.

So they look for slow/non growing surfaces.
Cell expansion might play a role also.

But in a well run tank, BBA is not present.
Slow or fast growing tanks.



Regards,
Tom Barr