Levels fluctuating

[iceman86]

I'm having some issues with my reef and it's causing me to loose sps on my 300 gallon system. My alk levels seem to fluctuate quite a bit. Mag is at 1320, cal at 420 and alk at 8. I'm dosing with a dosing pump 220ml of calcium and alk daily. I test mag and calcium weekly and they are constant but my alk remains constant some days, other days it doesn't get costumed so it shoots up my alk .5dkh if I don't catch it, within a few days it can crawl up and cause damage on my carbon dosed system.

I also recalibrated the doser to make sure it wasn't the problem. I'm using salifert test kits and the tank is almost 1 years old.

Any ideas?