Where did my algae come from?
Algae problems in an aquarium can never be traced to just one factor or general condition, and instead, are always the result of a combination of different factors, which include light, fertilization, water changes – specifically, how often and how much – feeding, fish population and, of course, the specific water parameters.
According to analyses that were performed over a course of a number of years, red algae, at least the common brush algae and beard algae, occur in descending order at the following parameters:
1) too little carbon dioxide (in relationship to 100 % of the measured tank); the pH level should be in the slightly acetic range, depending on the carbonate hardness, in every case.
2) elevated phosphate levels (over 90 %); phosphate limitation by means of JBL PhosEx ultra is often helpful here.
3) too little and too irregular fertilization (there should always be traces of iron at least).
4) insufficient water changes; a weekly water change of over 30 % is recommended for algae problems.
5) not enough fast-growing plants.