Is there a valve to prevent the return nozzle from sucking back water (Fish safety question!)

[An_Enemy]

I have a RedSea Reefer 250 and whenever I turn off the return pump to feed my fish, it creates a powerful vacuum when it sucks water back into the sump.
It makes me worried about the safety of the fish in my tank since the force is enough to tear a small fish in half if it gets too close.

Is there a one-way valve I can get that attaches to the return nozzle? I've seen check valves mentioned in some searches but it's hard to find reliable information.

To be clear, this has nothing to do with water filling the sump, that's not an issue, it's entirely to do with the sucking being dangerous to fish.

 

[GlassMunky]

I believe these are what you’re looking for

True Union Check Valve - Spears

Spears makes the highest quality True Union check valves. Use them to add a last line of defense against overflows. Check valves allow one directional water flow and are used to prevent back siphoning. They are commonly used on return pump outputs to prevent water overflowing the sump in the...

www.bulkreefsupply.com

they are known to fail after time though so are suggested you replace them once a year

 

[GlassMunky]

Your better option though IMO would be to position the return lines at the top of the water so when the pump turns off the amount of time and water that back flows is minimal to nonexistent.

 

[dank reefer]

Or drill a small hole in the return nozzle to break the siphon.

 

[kkelly007]

I have a RedSea Reefer 250 and whenever I turn off the return pump to feed my fish, it creates a powerful vacuum when it sucks water back into the sump.
It makes me worried about the safety of the fish in my tank since the force is enough to tear a small fish in half if it gets too close.

Is there a one-way valve I can get that attaches to the return nozzle? I've seen check valves mentioned in some searches but it's hard to find reliable information.

To be clear, this has nothing to do with water filling the sump, that's not an issue, it's entirely to do with the sucking being dangerous to fish.

This only works if you are manually feeding, but the return nozzle is a union joint (I’m sure you know this) and when I’m feeding or doing a WC, I simply move the nozzle up out of the water. You still get back flow through the gate into the overflow, but you’ll avoid the risk you’re taking about.