It's a problem on the tubes also when it's clogging them. I don't know who "they" is, but on the seachem bottle it says to dose daily. I appreciate your help, but you're obviously not asking for the information you need or you would have gotten it already.
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Re the dose, you are probably thinking of the Excel, being daily; I have never used this so I don't know what they (and yes, they means Seachem) recommend. But on the Flourish Comprehensive Supplement, is suggest 10ml for every 500 liters once or twice weekly.
I've never had brush algae actually clog the filter tubes; occasionally the small holes on the spraybar come close, but I remove them maybe every 3-4 months and use a little brush inside to clear them.
To work out the issue with problematic algae on the plants, one needs to know the tank size, lighting specs (tube type, kelvin, wattage, length, number), duration, fish feeding, water changes, tap water params, plant species, and fertilization. All these factors are inter-related and have to be balanced. When the balance between light intensity and nutrients is reached, and if it is just sufficient for the plant species, algae hasn't much of a chance. But when one factor is missing, the often-cited "law of minimum" applies, and plant photosynthesis slows and may stop altogether. This is when algae takes the advantage.
Usually the issue is too much light intensity, along with or perhaps just the duration. But it again all depends upon what is in the tank and what nutrients are entering it. But most times, reducing the light does resolve or help to resolve things. As an example of how delicate this balance can be, I used to see brush algae increasing during the summer, and it took me a couple of years to realize it was due to the increased intensity and duration of daylight entering through the windows. I now have blinds and heavy drapes over the windows all summer (I have a dedicated fish room so this is easy to deal with) and for the last three summers, no increase of algae at all.
Byron.
