Try and get it to around 8.5 dKh or so (slowly - don't dump a bucket load in at once).
What test kit are you using?
Once you have it where you want it, leave it a week and then remeasure. From the drop you should be able to calcuate what your "consumption" is which will help you figure out how much to dose.
For Algae it is a nutrient/Phos problem - look there. Also ensure you have plenty of flow. Sometimes people raise there Magnesium to battle Brysis (raising Mag to around 1250-1300 is a good idea as it helps balance the Ca and Alk out - stops it precipitating out of the water from memory - the little white "scum" ring you sometimes see at the top of the water level)
Remember Alk and Ca have to be in balance. Look for the graph by Randy. It will make sense.
http://www.advancedaquarist.com/2002/11/chemistry (notice the Alk units in the graph are not dKh so you will need to convert units - google it)