The root cause has been discussed to a greater or lesser extent in the following threads in which there were warnings of clear and present danger:
Please help on a new setup
does T5 has a maximum effective depth?
blue lights?
The common theme in these threads is the OP's hypnosis with light intensity - at the expense of all the other, more important factors that contribute to good plant health. This inevitably leads to the condition described in the first post of the thread
plants in a pail for the meantime? Is this okay?
For corroboration with Dusko's data, one can also check
JamesC's Algae Guide for a concise description of the root causes of Cladophora and some corrective actions.
No matter what we convince ourselves of, Cladophora knows when the tank is poor in CO2/Nutrients/Flow/Distribution for the given lighting level. The first step in combating any algae is to take stock of the light intensity. The more widespread the algal bloom the greater the indication that the lighting scheme is fundamentally flawed. If the hobbyist insists on keeping high intensity, then the other parameters must be raised in order to be equal to the task. CO2 and flow particularly must be high to support the massive growth demands of hostile and aggressive spectral energy levels. Dusko makes this quite clear in the article dated 9/19/2008 ("Algae Control") very near the top of the page.
It is entirely possible therefore for the lighting intensity to be so great that the required CO2 levels necessary to support the growth demand is higher than the toxicity threshold of the fish. High light creates a demand for high growth rates. High growth rates can only be sustained by high nutrient loads, high flow and high CO2 concentration. These are the links in the biochemical chain. Missing or broken links in this chain results in demolition of the system.
The best course of action is to lower the light intensity, and to add liquid carbon as well as to ensure proper dosing levels. This should knock back the Clado and return the tank to a more sustainable growth regime.
Cheers,
