Setting up Nano Tank with Dwarf Mexican Crayfish & Scarlet Badis

Nano Tank Setup

I set this tank up in May with a pretty specific goal in mind: Dwarf Mexican Crayfish sharing a small space with Scarlet Badis. Two species that don't usually get talked about together, but I wanted to see if I could make it work with the right amount of patience.

I cycled the tank for 6 weeks before adding anything. No shortcuts here. Seiryu stone, driftwood, and river stones went in as hardscape, with aquasoil as the substrate underneath. That combination is its own small balancing act. Seiryu stone leaches minerals and pushes hardness and pH up, while aquasoil pulls pH back down. Neither one totally wins, they settle into a kind of tug-of-war that the water chemistry ends up reflecting. I let that stabilize fully before stocking anything.

Equipment stayed simple: a sponge filter and a heater.

Planting first

Before any livestock went in, I planted rotala, water sprite, moss, and cabomba. This wasn't just for looks. The whole plan hinged on giving the tank time to grow in before adding a fish that could go after the crayfish.

Adding the crayfish

Once the cycle finished, the dwarf Mexican crayfish went in first. I wanted it established and comfortable. This species is small and slow-moving, so it needed the tank to themselves for a while to settle in without competition or predation pressure.

Waiting on the badis

I waited 3 weeks after adding the crayfish before introducing the scarlet badis. That gap wasn't random. I wanted the plants to fill in and mature enough to actually provide cover, since scarlet badis will pick off shrimp and crayfish fry given the chance. By the time the badis went in, the rotala and water sprite had grown in enough to give any future babies a real shot at hiding.

How it's going

No hiccups. No cycling issues, no pH crashes from the seiryu stone and aquasoil fighting it out, and no conflict between the crayfish and the badis. The slow, deliberate approach, cycle fully, plant first, add the crayfish, wait for growth, then add the fish, paid off. Everything's been stable since.

If you're thinking about mixing dwarf crayfish with a small predatory fish like scarlet badis, the sequence matters more than people think. Plant cover has to exist before the fish does, not after.