Here are some name suggestions based on your input:

Combining Elements:

• Basilius Blackscale
• Captain Koi
• Captain Blacksilver
• Bas Orange
• Blackscale Captain
• Silver Koi Bas
• Orange Basilius

Playing with Sounds and Alliteration:

• Blazer (combining black and silver)
• Oran (short for orange)
• Silas (combining silver)
• Koba (combining Koi and black)
• Capone (combining Captain)

More Creative Options:

• Obsidian Koi
• Emberglow (referencing orange and black)
• Nightsilver (referencing black and silver)
• Sunspot (referencing orange)
• Shadowfin (referencing black)
• Comet (referencing movement and orange/silver)

Mythological/Thematic Names:

• Kuro (Japanese for black)
• Gin (Japanese for silver)
• Aka (Japanese for red, but can be adapted for orange)
• Ryujin (Japanese dragon god, fitting for a Koi)
• Tenryu (Japanese celestial dragon)

This list provides a variety of options, blending your provided keywords and exploring different naming styles. Remember to choose a name that resonates with you and best reflects your Koi's personality.