dark green hairy algae?

[GreenIntentions]

so i have had my stem setup for about three months now and jsut started adding ferts saturday. all was going well untill yesterday when i noticed small tufts of hairy deepgreen almost blue hairy algae growing on my plants and only my plants. it isnt growing on any of my rocks or driftwood.

dose schedule

x1 flourish comprehensive
x1 flourish iron
x2 flourish potassium

and that was all since saturday after a 50% waterchange

light is 54 watt t5 6.7k hagen tube x2 over the length of the aquarium
55 gallons standard size 48 long 24 high etc etc
use a HOB filter no carbon just sponge
photo period before algae was 11-12 hours
no co2 or co2 additives such as excel

since algae ive dropped it down to 8, well today even with the reduced photo period the algae has seemed to get worse so im not sure what to do. the algae does rub off fairy easy but seems to be worse in the creveces of the plants I.E at nodes of the stems on stem plants and on rims of leafs.

[Kathyy]

Has the smell of the tank changed? It sounds like there was cyanobacteria or BGA in your change water if that is possible and this really is a brand new infestion. Well water maybe? I hope it cannot survive water treatment.

I saw those tufts sticking to the ends of leaves after I spent an hour airline siphoning out the sheets on every single surface in my 100 gallon tank. Bits would escape and they gathered there. It can grow that fast, my tank was covered again the following day.

If the tank has very low nitrates, low flow and debris gathering in crevices then fix all that. You might get lucky and it will go mostly away. I have it in my tank but it stays out of the way, I suspect there is enough nitrate and my biofilter is in pretty good shape. If not there is a particular antibiotic that can kill it. Loads of threads here on the subject, I don't recall the name or how to dose.

Your fertilizers don't have enough nitrate or phosphate for a bright tank and you will be in for more fun experiences with algae unless you cut back your lighting a great deal. Usually a 55 gallon tank only needs a single T5HO bulb and a lighting period between 8-10 hours. Using pressurized CO2 might let you keep the second bulb, might not.