try phos guard by sea chem or kents version. it wil remove phosphates and silicates as well as things that carbon will. get rid of carbon. buy a phosphate test. follow the instuctions on the can and test your water every other day. you will see the phosphate level drop and after some time it will start to rise again. keep track of this and use it to come up with a schedule for replacing with new without testing all the time.
for instance i replace my phosguard once a month. my tank is eighty gallons and i use 300g at a time. this costs me 7$ a month. not to bad. it keeps my phosphate levels below 0.1 ppm
problem cleared up in about 30 days. use a new tooth brush and water change to remove dead (dormant?) cyano
. dont try to do it all at one time. take your time, a little bit each week.