There is no visible water flow. Do my fish have enough oxygen?

[memorywrangler]

I'm worried about gas exchange/oxygenation.  Will the fish in my new 5-gallon have enough O2?

I have a new Fluval V all-in-one.   The way I have the pump setup, there is a great deal of flow through filter, but no visible water movement -- the surface is very still and flat.  This is how I want it because I would like to have floating plants.  The only real break in the water's surface is the "waterfall" into the filter compartment.  For aesthetic and power outlet reasons, I'd rather not run an air stone.  Will my fish suffocate?

More generally, I've heard conflicting things about what's necessary to have good O2 levels, so I don't really know how to think about this aspect of my tanks.  Any good guidance or references would be appreciated.  Also, are there any cheapish, reliable-ish tests for dissolved oxygen?  Something like a drop checker for O2 would be great.

[Guppysnail]

There are dissolved oxygen test kits. 
The best way to test is in the early morning before lights are on and before the room is well lit. Your o2 will be lowest at that time. Plants use o2 and emit co2 at night in the dark. 
 

This will tell you what your lowest point is. If it is too low then you know you need an airstone.

Hope that helps 

[Galabar]

The Fluval Spec 5 has a lid with a long hole in it.  So, the top of the tank is exposed to air fairly directly (I've got the Spec 3).

One interesting thing you can do is have the flow "circulate" your floating plants: https://photos.app.goo.gl/ACmLeJSzUQD7Pfso7

[nabokovfan87]

You can always use a ring of airline nto corral the floating plants. There should be some surface movement.

[tolstoy21]

On 8/11/2023 at 7:02 PM, memorywrangler said:

The only real break in the water's surface is the "waterfall" into the filter compartment.

I would imagine this is sufficient. I had a fluval spec V a while back and never had problems with O2 exchange. You can also point the return up a little so that also makes a small amount of ripple on the surface.

[Galabar]

On 8/12/2023 at 4:04 AM, tolstoy21 said:

I would imagine this is sufficient. I had a fluval spec V a while back and never had problems with O2 exchange. You can also point the return up a little so that also makes a small amount of ripple on the surface.

Yes, definitely do this.  I've got both my Fluval Spec 3 and Lifeguard 4 gallon doing this.

 

[memorywrangler]

Thanks for the suggestions, everyone.

 Pointing the pump outlet at the surface created a lot more surface movement than I wanted, so I ended up building a little airlift pump instead.  The fish seem happier with the gentler flow.