Question About Water Flow

[stanleo]

While I am researching corals and I come across water flow descriptions of low, medium or high and I am confused. I'm not sure how to even word this question. How is each achieved? How do you know if the water flow is low, medium or high? Is it high when you place a coral right in front of the powerhead? That seems too high to me. Is it low when the filaments don't sway at all? Can someone unconfuse me please? Thanks

 

[sputnick]

Well I think the average flow rate of an aquarium is 20x turnover rate. This leads  me to believe that anything under is low, and anything above is high. But like you said It could also depend on where the coral is placed in the flow. behind a piece of rock will slow the flow but placing the coral infront of the powerhead will be lots of direct flow.

 

[Donya]

Flow is a fuzzy thing. For the more common tank sizes and build strategies, I usually think of it as:
10x = low flow. Won't work in many tanks.
20x = medium, the norm.
30x = high flow. In smaller tanks like nanos, there are likely to be zones where fish have to navigate a bit carefully when there is this much flow.
40x+ = insane flow. Your fish will wake up one morning and wonder why they're not in Kansas anymore.
 
BUT...it is dependent on tank size and shape as well as whether you have any pumps pointed at each other to create chaotic movement (less net flow even if the gph rating is high). You can easily get big tanks that require higher flow because there are more obstructions present (more rock stacks) that hinder the flow. I could easily see a 200gal requiring 40x flow. But, most people don't have 200gal tanks.
 

Is it high when you place a coral right in front of the powerhead?

 
It will be locally high of course, but also linear. Generally, strong linear flow is best to avoid. Alternating or swirly patterns are more natural; you don't want polyps all flattened in one direction. Linear flow can actually be used on large anemones as a trick to make them pick up and move elsewhere in the tank.

 

[stanleo]

So when they are talking about low, medium or high, they are talking about the overall flow in the whole tank? I thought it was talking about the flow of the current that is going over the individual coral? I thought this was about the placement of the individual animal. Am I thinking of this in the wrong way?

 

[sputnick]

So when they are talking about low, medium or high, they are talking about the overall flow in the whole tank? I thought it was talking about the flow of the current that is going over the individual coral? I thought this was about the placement of the individual animal. Am I thinking of this in the wrong way?

Well actually i believe its both. You need to have good flow in your aquarium for filter feeds to bring food to them. Others like less flow and will do better in the lower current areas of the tank. Remember your tank will have its own current path, where some areas have high flow, other areas will have medium and low flow. So its not just over all tank flow but also where they are placed in the tank