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Sugars in aquarium

M

Marcel G

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In my two tanks I struggle with biofilm on the water surface. It's not something really that bad, but I observed that when I use aerating at night, the next day the biofilm is gone. As I studied the problem more deeply I found that the biofilm is kind of protein or sugar film. Maybe there are more kinds of "biofilms" ... some from proteins, others from sugars (I don't know). My case seems to be more of sugars, because whenever I use aerating, the biofilm is gone. And as you probably know sugar is a food for bacteria, which need a lot of oxygen to transform it into CO2 and water (with alcohol or lactic acid as chemical intermediate/by-product). So it can be that if you don't have enough oxygen or you have big production of sugars in your tank, you have a biofilm or cloudy (milky) water.

I would like to know if someone have any experiences or can explain what could be the source of sugars in our tanks ... causing these biofilms and/or cloudiness?

My plants seems to be in a good condition, I have a decent light (70 µmol PAR at the substrate), big external filtr, good circulation, dosing EI, changing 50% of water + doing regular maintenance each week, not overfeeding my small group of fish, adding CO2 via reactor with green-yellow dropchecker. My plants seems to be healthy, although the Ludwigia is dropping some bottom leaves from time to time (probably because the light doesn't get to the substrate in some parts too well).

What should I do to solve this little "problem"? Thanks in advance for your replies.
 
Plants leak sugars and other carbohydrates into the water column all the time. Any aqueous environment will develop a biofilm which consists of not only carbohydrates, but also of proteins and lipids. Every wetted surface has a biofilm. Algal spores as well as bacteria and a host of organisms live in the biofilm. In some aquatic systems in the world, more than 50% of the total biomass of that system is actually in the biofilm.

In a tank system a thin biofilm is expected. The film buildup is a natural part of the metabolic waste produced by flora and fauna. If the tank is healthy, this normal amount is easily controlled by disturbance of the surface. Changing the position of the filter outlet to disturb (but not to break) the surface can keep this in check. However, when the biofilm thickness becomes excessive it can be an indication that the plants are not healthy. Unhealthy plants leech greater amounts of carbohydrates, proteins and lipids when they are suffering stress, so this is an indication that lighting is too high for the level of either nutrients, CO2, or flow distribution being administered. more discussion on Surface Film | UK Aquatic Plant Society

Cheers,
 
Thank you, Clive, very much for you reply!
 
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