Rainbows & Goldfish together?

[Akshay]

Has anyone ever kept Dwarf Neon Rainbows (Melanotaenia praecox) with goldfish?

I have 4 fancy goldfish (either Fantails, Orandas, or some sort of hybrid of the two). They are around 4–5 inches each. I also have a school of 8 Dwarf Neon Rainbows in another tank (2 males, 6 females).

The rainbows are super sensitive to CO₂. The moment I cross around 30 ppm in my planted tank, I can see them struggling, so I’m thinking of shifting them to the goldfish tank, which has no CO₂.

The goldfish tank is 300 litres (4 × 2 × 2 ft / 80 gallons), and the rainbows are around 1.5–1.75 inches.

Usually people say no to goldfish tank mates, mainly because of a mismatch in temperature or temperament. But in this case:

• The goldies cannot possibly eat the rainbows at their current size.
• The rainbows don’t fin nip, or at least I’ve never seen them do it.
• The water parameters in both tanks are quite similar.
• Goldfish tank: GH 6, KH 2
• Current rainbow tank: GH 4, KH 0
• Temperature is pretty much the same in both tanks: 24–25°C (74–77°F).

Has anyone actually tried keeping Dwarf Neon Rainbows with fancy goldfish? Any issues I’m overlooking?

 

[Koan]

The other thing I'd think about is the filtration on the goldfish tank. What are their baseline nitrate levels?

Since goldfish are just fancy carp and are so heavy-bodied for their size, they put out an enormous amount of ammonia waste. Because they are carp, they evolved to dig around in nitrate-rich swamp water, and their gills are set up to manage in higher nitrate environments.

Rainbowfish are none of those things I would expect your praecox to be quite a bit shorter lived in their environment unless you have superb filtration.

Everything you ever wanted to know about the physiology of nitrogen management in different kinds of fish

https://journals.physiology.org/doi/full/10.1152/physrev.00050.2003

https://www.sciencedirect.com/science/article/pii/S0048969723038354

 

[Akshay]

The other thing I'd think about is the filtration on the goldfish tank. What are their baseline nitrate levels?

Since goldfish are just fancy carp and are so heavy-bodied for their size, they put out an enormous amount of ammonia waste. Because they are carp, they evolved to dig around in nitrate-rich swamp water, and their gills are set up to manage in higher nitrate environments.

Rainbowfish are none of those things I would expect your praecox to be quite a bit shorter lived in their environment unless you have superb filtration.

Everything you ever wanted to know about the physiology of nitrogen management in different kinds of fish

https://journals.physiology.org/doi/full/10.1152/physrev.00050.2003

https://www.sciencedirect.com/science/article/pii/S0048969723038354

Yeah I should have mentioned
My NO3 never ever climb over 10 ppm and that is with dosing macros daily in the tank

Filteration, currently FX6 but building a sump (around 100 ltrs) for this tank

Will transfer (if I do) rainbows after the sump is built and will reduce no3 in the macro blend

Thank u for the links, will be reading them tonight for sure

 

[Kwyet]

I don’t know about that, but the rainbows can adjust to higher CO2 if you increase it gradually over several days. Mine are doing fine at around 45 ppm.