Why does my rainbow only sometimes colour up

[aqariumclements]

Have an all rainbow species tank however a couple of the rainbows only sometimes have colour, they're not dull but appear almost silvery then when coloured up are a brilliant dark orange and black colour, I am not aware of the type of rainbow this particular fish is and I believe it to be some form of hybrid!

 

[Brookster123]

I had rainbows briefly and I remember them being brilliantly colored up in the morning and during mating behavior..

 

[aqariumclements]

Will also add that this is a newly set up tank that is the processes of cycling all parameters are zero with nitrites showing 0.2 also the pictures do not give the fishs colour justice in these photos but show him when he is in colour

 

[aqariumclements]

Hey brookster how are you, yeah they look magnificent first thing on a morning and around dusk on a night, howcome only briefly did you have any problems with keeping them?

 

[Brookster123]

I'm good! Thanks! How long has tank the tank been running? I brought then back after a few months because they seemed to active for my setup.. Beautiful fish though.. Yellow rainbows..

 

[aqariumclements]

Erm I'd say around three weeks now maybe more, I've put used filter sponges Inside the internal filter from another cycled tank to hopefully speed up the process! Yeah they are extremely active would the get along with Cory catfish?

 

[Brookster123]

Ohh good, sounds like you're just about cycled then.. I think Cory's would good tank mates, they should all stay out of each others way, just make sure the Cory's eat, rainbows are rocket pigs!