Wema gauge
I have the same gauge on my boat. It is made by Wema. They also make water tank gauges, volt, amp and all other kind of guages. They have a replacement tube that can be cleaned by back flushing it while it is still installed which I have bought as a spare but not installed yet. For what ever it is worth though, I had to clean mine about every year till I started to squirt a small amount of Dawn dish soap into the tank every time I pumped out. The soap breaks down the oils and seems to prevent the holes from plugging up. I am now on my third year with out a cleaning and it works perfectly. I am very satisfied with the Wema systems will probably put the same in my next boat if and when that ever happens. Do not give up on the wema gauge, it will easily out last the head that pumps the stuff in there.