"blanket" algae problem

My tank which has been established with no changes in care, plants, filter,
cleaning for 5 years has all of a sudden got an algae problem. It is a dark
green algae that blankets itself across the stones. Nothing on the plants
or glass. I've done two 20% water changes within the past week. I changed
the filter product, but not too closely to the water changes. I have spot
cleaned the tank of all algae, and overnight the algae comes back. What
type of algae is it? What could be the reason for it when I have changed
nothing at all? And waht should I try to fix this problem? I do have a
water test kit, and I will do a test on whatever one thinks the problem
might be.

On Feb 3, 6:32*pm, "Christie" wrote:
My tank which has been established with no changes in care, plants, filter,
cleaning for 5 years has all of a sudden got an algae problem. *It is a dark
green algae that blankets itself across the stones. *Nothing on the plants
or glass. *I've done two 20% water changes within the past week. *I changed
the filter product, but not too closely to the water changes. *I have spot
cleaned the tank of all algae, and overnight the algae comes back. * *What
type of algae is it? *What could be the reason for it when I have changed
nothing at all? *And waht should I try to fix this problem? * I do have a
water test kit, and I will do a test on whatever one thinks the problem
might be.

It can be caused by an excessive amount of buildup of detrius in the
gravel or substrate. Do you vac the substrate? It is commonly called
black algae, as its so dark green in color sometimes it looks black.
Have yu changed your florescent light tubes lately? Often times when a
bulb gets some time on it (years or months) its not uncommon for the
light wave to change intensity and can create algae. It takes light,
and nutrients in the forms of nitrate and phosphates toget algae
growing, so I owuld check my water for an excess amounts of nitrates
and phosphates. They make phosphate removers in chemical and filter
batt media form that does a fair to great job. One that does work fine
is simply called Phosphate Sponge..............You can also be fueling
the algae with what and how much yur feeding, and if somehting has
changed in yur water supply, as its not impossible toget higher
nitrate or phosphate levels due to run off and how the water is
processed and where its obtained from, and all it takes is a bit extra
to start and fuel algae blooms as such.............With it starting
and staying on ther gravel it leads me to believe yu may have
excessive nutirents in the substrate that has built up over the years
or perhaps lighting (bulbs) may need changing.