Question about Kalk/Auto top off

[BCOrchidGuy]

A number of people drip kalk after lights out, how do you control the drip to turn it off during the photoperiod? I can understand a float switch but wouldn't that add kalk to quickly? Maybe I'm missing something.

Thanks, Doug

[Delphinus]

Here are some ways I could think of:

1) Use a dosing pump, such as a peristaltic type (e.g., http://oceanaquatics.com/store/product/202/AquaMedic-SP-3000-/ ), or a metering pump, or any kind of low-volume pump (e.g., http://www.premiumaquatics.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=M3-AQUALIFTERPUMP&Category_Code= ) , on a timer (might still want to use a float switch in tandem for extra security - i.e., shutoff if level reaches set height)

2) Use a solenoid valve (like for irrigation) on a timer and gravity feed with a float valve (again so as to not overfill)

3) This is probably more like #1, but a little powerhead on a timer to feed a tiny bit of pressure into a kalk mixer or a kalk reservoir, and an irrigation dripline valve to throttle back the driprate.