Spirogyra - Silk Algae, Water Silk

This non-branching green filamentous algae is called Spirogyra. This algae doesn't appear in polluted water systems but in ones that are eutrophic, rich in nutrients (liquid ferts, CO2 and light).
It grows very fast, forming long, entangled strands. I would personally call this one the "spaghetti algae" :-) , the way it looks to me. I am not sure algae eaters will eat Spirogyra. This aquarium of mine has Otocinclus and Neritina Zebra snail, and they are not showing any interest in eating it.
I have removed this algae manually, very easy really.

Since the beginning of this set-up I have used the Estimative Index fertilising regime, dosing 2-3 times a week N,P,K, traces and liquid Carbon (Easy Carbo), so I don't think any nutrients were missing.
There is one problem I have caused (I assume). Instead of performing 50% weekly water change I did 25% every 2nd or 3rd week. I wouldn't say that irregular water change induced this algae but dirty filter (I clean filters with each water change). The filter gets dirty and reduces the water circulation. Less circulation = slower nutrient transport. Also weaker surface agitation = less Oxygen.
I did some tests by doing water change every 3-4 weeks but cleaned the filter every week to keep good flow and moderate surface agitation and this algae never came back.
So keep your filters clean ;-)

Photos by Dusko Bojic.


Surface Scum/Film (edited May6th 2010)

This is a protein bio-film, probably triggered by hi organic levels, poor circulation and low CO2 levels.
Neuston organisms readily develop in it (or underneath it), like bacteria/zoo-spores/protozoans, hydras, worms even small snails.
This scum is very compact and often green. It is impossible to break it with the finger. I have tried it, and the film just grows back together in a second. Visually it appears "oily".
I have removed the film by using paper kitchen towels, laying them over the surface many times, until the scum was gone. After that I have performed a huge 80% water change, rinsed the filter media very well (that in fact was dirty) and have introduced one extra filter pump (extra circulation and surface agitation).
Also, I started using Easy Carbo (like Excel) instead of the CO2.
Everything seems to be in order now.
One more thing, I didn't prune plants in a long time so they covered the entire surface. And because of that, the tank circulation was poor, causing probably lower O2 levels as well. All this induced the surface scum.

There is another type of surface film caused by the Eisenbacteria (Iron bacteria). This film appears to be whitish, much thinner and breaks easily on touch. Improving surface agitation will help in combating this kind of film.

I have fixed this surface film (white and green) in 3 different tanks by simply introducing an air pump or aplying the venturi air diffuser to the power head (without removing it the film would disapear by the next day). The air bubbles seem to be breaking the surface tension causing the surface film to break into tiny particles which sink to the bottom or get trapped in the filter (in both ways bacteria will break them down).

Photos by Dusko Bojic.

Cladophora algae

Cladophora is a branching, green filamentous alga, that forms a moss like structure. This algae doesn't appear to be slimy. Threads are very strong and very thin. It grows on rocks and submersed wood exposed to direct light, in very bad cases will grow on plants also. Usually it tend to stay on one spot, which makes it easy to remove. Comb it and dose more CO2 and improve water circulation for better nutrient transport. In a case where Cladophora takes over the grassy plants, mow the plants like the lawn. No algae eater is known to eat this kind of algae.Photos by Dusko Bojic.