HOB overflow question

[astreck827]

Hoping someone with experience using HOB overflows can give me some insight. I am setting up a side Fuge to grow out some macro algae and want to use a HOB overflow box. I have a used CPR overflow but it’s way overrated for what I want to do. It can handle up to 1500 gph, but I’m only setting up a 40 breeder and don’t want to run that much through it. If I use an aqua lifter, will it be a problem to undersize the pump? Is there a minimum % of the max flow that needs to be reached, or a way to slow down the siphon?

 

[AquaBen]

I have a similar set up. The rate of siphon flow is controlled by the size of the siphon tube(s). If you don't want a lot of flow then use a smaller siphon tube. Then size your return pump to match that flow. For me I was surprised how little the flow was -- I had to downsize my return pump. My display is 65 gal. My fuge is 15 gal. I couldn't tell you what the rate of flow is. As you can see my siphon is comprised of clear tubing with pvc corners. The seals are not perfect and a small amount of air trickles in which reduces the flow. Once a week the flow gets low enough that the level of the sump gets too low and the return pump starts to suck a little air. I have to use a small air line to suck out the air and reestablish the siphon flow. I could glue the siphon pieces and put an end to the air leak but I like being able to take it apart for cleaning. Until recently the only things in my sump were ceramic tubes I used for a bottom and the cheato, together with a few snails and hermits.. I added an order of pods after about six months and they have taken off well. I just added a Rollermat to the equation last week. Attached are a couple of pics showing the HOB set up. Adding a refugium was definitely a quantum upgrade to the health and beauty of the display tank.