Livestock selection is a critical part of planning out a system. This should be done well before any money is spent.  It can determine all the requirements: tank size, flow, lighting, and nutrient control levels.  Included in the livestock selection should be some mandatory critters to help naturally maintain the system for algae and pests.  I personally always include a selection of these for every tank I own and use this as a quick short list.  But keep in mind that manual removal of unwanted tank inhabitants by the hobbyist should still be part of basic maintenance.

Clean Up Crew for Specific Algae

I would recommend to add these slowly, a little at a time based on what you are battling to avoid overcrowding. If overstocked they will starve (without supplemental feeding ) and die polluting the water.  I personally avoid hermit crabs since they can be opportunistic and start attacking your snails when they grow too big. Select a wide variety to cover all bases.

• Diatoms – Conch, Cerith, Trochus, Nerite snails
• Detritus – Conch, Cerith, Trochus, Nerite, Nassarius snails, Tiger Tail sea cucumbers, brittle starfish
• Film Algae – Astraea, Turbo, Ceriths, Trochus, Nerite snails, copepods
• Cyano – Cerith, Trochus, Nerite snails
• Fine Hair and Turf Algae – Conch, Astraea and Turbo snails, Blennies (Algae, Bicolor, Tail spot etc.), Hectors/Rainfordi gobies, Lettuce Nudibranchs and sea hares, urchins (tuxedos preferred), various mouth shaped Tangs (for appropriate sized tanks), small blue leg or scarlet hermit crabs
• Bubble Algae – Emerald Crabs, Fox Face Rabbitfish & Sailfin tangs(for appropriate sized tanks)

Pest Control

Biological pest controllers are great since they will be constantly patrolling for their next meal, but be forewarned that every specimen may not always prefer them, especially if they are fed too well.

• Bristle worms: Coral Banded Shrimp, Arrow Crabs, Pseudochromis, Dottybacks, reef safe wrasses (6 Line Wrasse, Yellow Coris Wrasse, Melanurus Wrasse, Leopard Wrasse, Green Bird Wrasse), File Fish,
• Aiptasia – Peppermint Shrimp, Berghia Nudibranchs, Aiptasia Eating Filefish, Molly Miller Blenny
• Vermatid Snails – Bumble Bee Snails , Possum and 6 line wrasses
• Polychaetae worms (spaghetti worms) – Bumble bee snails,  reef safe wrasses, Sand-sifting fishes like the Diamond Goby, Arrow crabs, and Sand-sifting starfish
• Asterina Starfish – Harlequin Shrimp
• Acropora Red Bugs – Dragon Face Pipefish
• Red Planaria / Flatworms – some reef safe wrasses, Mandarin, Yellowtail Blue, and Springeri Damsels
• Montipora Eating Nudibranchs – Reef safe wrasses
• Zoanthid Eating Nudibranchs – Reef safe wrasses
• Pyramid Snails – Scarlet Pin Stripe, Yellow Coris, and 6 line wrasses
• Fish Parasites – Various Cleaner wrasses and gobies, Cleaner Shrimps