Rubble would be great (ideally from your display tank) and it will help with any ammonia formation. Since the mandarin is in a small tank, you have to be sure you have enough biomedia in the tank to convert the ammonia away.
We are going to overnight a care package for you, it should help keep the little guy well fed.
Dragon Roe - Awesome Roe that is perfectly sized for the captive bred mandarins.
Dragon Roe AlgaeBarn Dragon Roe Frozen Food is the perfect food for any finicky fish, especially mandarins! Rich in important Omega 3 fatty acids, it is an incredibly wholesome and natural component in any reef aquarium diet.
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Can o Cyclops - Preserved copepods.
Can O' Cyclops by ZooMed provides excellent nutritional value for small fish, such as the Biota Captive Bred Mandarin. These preserved copepods are similar in appearance and size to live adult copepods; therefore, encouraging a fantastic feeding response.
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Simple Brine - Decapsulated hatching brine shrimp cysts
AlgaeBarn Decapsulated Brine Shrimp Eggs AlgaeBarn Decapsulated Brine Shrimp (Artemia salina) Eggs make live food culture from home simple and convenient. Safer, more nutritious and completely free of pathogens, decapsulated eggs are always the best choice.
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EcoPods - Our 4 species blend of copepods :-D
Each 16 oz portion of EcoPods contains an ecologically balanced consortium of copepods including Tigriopus, Tisbe, Apocyclops and Oithona. All of our pods are 100% viable to reproduce in marine aquaria, including Oithona.
www.algaebarn.com