My neons like still water . . .

[Mcostas]

So I do the soap dish trick. It attaches with suction cups and has big holes on the bottom.

I cut a piece of water polishing membrane (size 100) and fluval bio media in it.

As it is now the water is completely still. When the filter material gets clogged it will overflow a little. 100 pore size is pretty small, I wish I got 200. But even with overflow it makes the water noticably clearer. Every few days I take the piece out and spray it under the faucet, it's not a biological filter, it needs to be clean.

By altering the media in the dish and by raising or lowering the dish you can get a little water movement. I have it up high and for now the water is all going out the bottom.

The neons love the still water. I had at one point a small sponge filter (it was for the shrimp but they died) in the middle front and the neons tolerated it but I couldn't move it, it disturbed their shoaling spots.

Only problem is the surface gets a little scummy from the absolutely still water. I can shift the pump or dish to get a little movement. They really seem to love the still water though.

Here is a top shot and a shot from the front. The filter is an aquaclear 30.

 

[AbbeysDad]

That's an interesting secondary filter setup. What's inside the Aquaclear filter?

Many hobbyists have fish that in the wild often live in fast moving streams so they attempt to duplicate flow. In fact, although of course there are some wild caught fish from the Amazon and Rio Negro rivers, many are bred and raised in tanks or ponds and never see fast flowing waters. I imagine that it takes a lot of swimming energy to live in fast water, so I'm sure that many fish do better in calmer waters.

 

[Mcostas]

The aquaclear has a foam block on the bottom, a filter cloth on that (100), bilomedia next, a filter block on top that's cut in half with a finer filter cloth (50).

I'll probably reach a point where I remove the filter cloth eventually. It clogs rather quickly. Does a great job though.

 

[AbbeysDad]

I discovered over the years, that commercial bio-medias just didn't live up to their marketing hype. So all of my filters (4 Aquaclear HOBs and 1 HW 304B canister) are filled completely with sponge material as sponge is not only excellent at mechanical filtration, but also excellent at biological filtration. This can be objectively evidenced by large fishrooms that run exclusively on air driven sponge filters.
Further, when I was young and [more] foolish, I thought we should clean filters often to get the 'crud' out of the system. In time I learned that valuable beneficial bacteria and microbes develop and mature in the filters (and the substrate) and disturbing this with excessive cleaning is counter-productive. These days I only clean filters when output flow is noticeably reduced...and then the cleaning is merely enough to ensure a decent output flow.
....live and learn.
Here's a deep dive into Filtration and Water Quality.

 

[Mcostas]

Originally the soap dish was just supposed to break up the current, I put attractive rocks in it but they were too heavy. The smaller media was too small and fell through the holes so I put the filter material on the bottom and the "biomedia" over that.

I didn't think of using the sponge, I wonder if it would be too light and float out?

At any rate, I have plenty of sponge in the aquaclear. In my other tank (10 gallon with Betta) I have a topfin that uses cartridges, so I run a sponge filter a couple weeks before I have to change it. She's a little female koi and doesn't seem to mind the current as much as the neons. It's adjustable, I turn these filters up for a few hours a day, just for better filtration.