Sometimes and oftenly with high power led lights depending on how much you have hanging above your little tank the light intensity might be a bit on the high side. Then you might shorten the periode in hours but this doesn't alter the intensity and you still might be in trouble. Many times when fighting an algea isue, to much light in periode and in intensity is the most common culprit and lowering it helps to fight it off better. Then with no dimmer installed most people put frosted transparent material betweem lights and tank or use surface vegitation to lower the light intensity.. These are somewhat drastic measurments which are hard to regulate with. It's there or it isn't and nothing in betweem. As you said your self, "maybe i need to solder some leds off". Now with a dimmer you don't need neither of the above nor need to solder anything off. You regulate the light intensity with the turn of a button for the whole periode. In time when your balance is slowly returning and your plants are maturing you might slowly up your light intensity again with little steps over a periode of time and easily go back again if you see you're on the turning point of algae development again. This is much easier to regulate then going up and down in steps of maybe 30% at once with taking dimming materials away or scooping off surface vegitation or soldering a number of leds back on. That's the advantage in investing and installing of a dimmer, no matter what kinds of lights you are using. Smaller and shallower tanks are prone to get to much light especialy with the use of high powered cree leds. Unfortunately these leds need to be dimmed with a dimmable power supply which are more expensive then dimming controllers for non cree leds. So i can understand that this makes you reluctant in investing in one. If it is a necessaty? I guess it's personal preference in how you like to do things. For me it is, because im also over powered when it comes to lights and there for i have one.