Sponge filter causing surface upset. How to curb this?

Hi,
Breeding bettas. New sponge filter (rated 10-20 gallons, being used in a very slightly more than half full 20 gallon long, lift tube cut so that the output is about 1.5inch below waterline) is causing reasonable surface upset. I need the surface to be stiller for my male to make his bubble nest. Putting a peice of sponge or something in the top of the tube would probably lessen the power of suction and the efficiency of the filter a lot. HOB filter not an option b/c water needs to be pretty still & there will be betta fry that could get stuck in the intake. Plus I want the bubbling for oxygenation.

What should I do? Anything? The sponge filter's bubbles are just kinda making the entire water surface ripple and wiggle.

 

You could do a HOB that has an adjustable flow and add a sponge on the intake (there are special ones for that). It's what I use for my guppies.
You could also replace the HOB media with a sponge to slow the water down. That's what I do for my male bettas tank.

Not sure what to do if you keep the sponge filter

 

You could do a HOB that has an adjustable flow and add a sponge on the intake (there are special ones for that). It's what I use for my guppies.
You could also replace the HOB media with a sponge to slow the water down. That's what I do for my male bettas tank.

Not sure what to do if you keep the sponge filter

I would like to keep it so I don't need to do a filter shuffle or buy anything new, but maybe I might just need to suck it up.

Do you think two smaller sponges on a T valve would produce finer/less disturbing bubbles?

 

It might, do you have a smaller air pump lying around? That might also work

 

I do, the one it's on is a 20g pump, I have one meant for 5 to 10.

But for real the 5 to 10 one feels stronger lol. I could also just grab a buttload more tubing and make the tube to the sponge redundantly long to buffer flow

 

If it's cheap and it works it's definitely worth a try

 

If the air flow through your sponge filter is causing excessive turbulence, the first thing to do is try to reduce bubble size. Place a small airstone on the end of the airline inside the sponge. Smaller bubbles will make less turbulence.

If you cannot fit an airstone inside you sponge, the alternative is to reduce the air flow to the sponge filter. Some air pumps have adjustable air flow. You can also add a needle valve in the tubing to control flow, but be aware that the increased backpressure on the pump will shorten the life of the pump diaphragm and flapper valves. Another option is to add an air bleed so that some of the air from the pump escapes and less goes to the filter, but that can be annoyingly noisy if the tank is in a living area.

 

Could you put in some floating plants? Or maybe a ring of airline tubing on the surface above the filter to dampen waves from travelling beyond that area?

 

The airline ring is a good idea and really helps in the reduction of flow. I believe I have seen fishkeepers using disposable soda cup covers, feeding the airline tubing through the cross-cut in the center, and let the cover float on the surface.

 

A ring of air line does help a bit .
Two outlets in this tub. The hose stays in place with just the bubbles.

 

I have a cheap solution that might work for you. Take the lid from a take-out drink, feed the air line through the hole for the straw, and let it float on the surface. I use that to keep water from splashing out of the tank.

By the way, I'm not smart enough to figure that out on my own. I saw it on one of LRB Aquatics Youtube videos.