Are Phosphates Bad?

[keastclan]

Hi All, 
I have an ongoing problem with green cyanobacteria in my planted tank since the back end of last year. I have done numerous blackouts etc which temporarily gets rid of it but it keeps returning. Also bought a powerhead to get rid of dead spots.
In the UK you can't buy antibiotics to get rid of it, and besides I don't want to kill off my good bacteria. 
 
I went to my LFS last weekend with some tank water and tap water and they tested for everything and said that my phosphates were high. The phosphates in the tap water are fine. All other readings were fine. They checked that I wasn't overfeeding etc. 
 
So they have advised 10% water changes for 2 weeks and then take back another sample to be tested. 
 
The cyanobacteria does seem to be receding (or is that wishful thinking)
 
I thought phosphates were essential for the plants?
 
What causes them?
 
If this is my problem how can I keep them at bay without doing water changes every day?
 
I do have confidence in my LFS, but thought it would be as well to check on here too

 

[frapadoodle]

Well Phosphates in and of themselves are not bad. But in higher amounts they lead to algae outbreaks.
As for where they come from. Fish waste, decaying plant material, various foods have phosphates in them. Plant ferts, tap water, water buffers, et cetera.
There are a couple of chemical treatments out there.

 

[fenny666]

Hi. Removing dead spots in a planted aquarium is a necessity to ensure nutrient distribution, so a power head will certainly help.
Adding fast grow plants such as hygrophila polysperma(nice plant and easy to grow) will help consume excess nutrients.
Although getting to the source of the problem is always preferable you can spot treat with 3% hydrogen peroxide. Check out youtube on how to do this.