Food Coloring?

[Kaosu]

I think that's a super D duper idea!!!!

they already said they did it...just wanted to see...

 

[fishmamma]

they already said they did it...just wanted to see...

Like it's not blue anymore?

 

[GolemGolem]

I don't think he's coming back....

 

[aclockworkorange]

Maybe he decided to take a mass quantity of food coloring to test it... And died.

 

[Gatorxxx420]

Something tells me a good dark background and dark substrate with a blue or red light could achieve the look the OP is going for without harming the fish in any way. Doesn't sound like the greatest of ideas for sure.

 

[aclockworkorange]

Blue LEDs...

 

[ecoli73]

Blue water does not look nice...blue lights on water look nice.

 

[Kaosu]

found this...
http://www.koiandpondinc.com/Solutions.htm

 

[fishmamma]

Blue LEDs...

This does look nice, is this yours?

 

[HuffDaddy]

5 Gallon