What are some filters I can build alongside my undergravel filter?

[Blackwater guru]

These are the images of my recently established freshwater 140 liter tank located in a dark corner in my dad's home office .

In total the tank has 10 wild caught cardinal tetras and 4 corydoras duplicareus catfish and so far they have been looking healthy and active preferring to stay in groups.

I am currently running an undergravel filter connected to a pump through the pipe structure in the image.

As of now the tank is going through the fish in cycle and sometime during late january or early february the tank will have finished it's nitrogen cycle which is when I will add xray tetras.

My end goal here with this setup after a few months is to turn it into a blackwater setup with floating plants as seen in the above images and pieces of wild caught birch driftwood and dried oak leaves at the bottom.


I have also been thinking of possibly complementing my undergravel filtration with extra filration to help support the undergravel filtration and that I can actually build my own filtration.

I am just not sure what types of filters I can build because the water flow has to remain slow and I am not sure which ones would fit the best in a blackwater setup.

 

[Retired Viking]

Have you considered using tetra safestart plus to cycle your tank? I have under-gravel filters in my 55 and 30 gallon planted tanks. I have been thinking of using a sponge filter in the future. They are simple and effective.

 

[FallenPepper]

Tank looks great! A sponge filter never hurts though it can look out of place in a more open tank but an under gravel filter on its own should be good

 

[Blackwater guru]

tetra

Have you considered using tetra safestart plus to cycle your tank? I have under-gravel filters in my 55 and 30 gallon planted tanks. I have been thinking of using a sponge filter in the future. They are simple and effective.

I was originally gonna use something like that then I realised if I do a fish in cycle I still get to see the fish.

I have not seen the product you mentioned in the local fish store I do know I could order it online but my card won't even allow online purchases.

A sponge filter might just be a good idea and I will look more into it later.