Following on from Opcn's comments here is some info from www.liveaquaria.com regarding the individual fish so that any potential interested parties know what they are letting themselves in for. It is all too easy to be tempted by free fish and not to bother checking them out:
Hovercraft Boxfish (Ostracion cubicus) -
- Minimum tank size = 125g
- Maximum size in aquarium approx. 18"
- When first introduced, the Cubicus Boxfish prefers a diet of live brine shrimp or bloodworms. Once acclimated, the diet should include chopped squid, clams, mussels, and herbivore preparations
- This is a very difficult fish to keep in the aquarium setting by any other than the most experienced aquarist
- If stressed, the Cubicus Boxfish releases a poisonous substance, called ostracitoxin, from its mucous glands which will kill other fish in the tank very quickly
Cowfish (Lactoria cornuta) - (Took a guess on which particular one it was)
- Minimum tank size = 125g
- Maximum size in aquarium approx. 16"
- Since they are omnivores, the Cowfish Longhorn should be offered a variety of meaty and vegetable foods. They are slow eaters, and should not be housed with aggressive eaters
- When possible, the Cowfish Longhorn should be the first fish introduced in the tank
- Similar to other boxfish, the Cowfish Longhorn's skin is poisonous and, when threatened, it will release a toxin lethal to other tank members, including other Longhorns
Mandarin (Synchiropus splendidus) -
- Minimum tank size = 30g
- Maximum size in aquarium approx. 4"
- It should be kept in a well-established 30 gallon or larger aquarium with 75lbs+ of mature live rock and plenty of hiding places
- It feeds on a variety of vitamin-enriched live brine shrimp, live black worms, and natural prey on live rock and live sand therefore a good population of pod life is required
Humbug Damselfish (Dascyllus aruanus) -
- Minimum tank size = 30g
- Maximum size in aquarium approx. 4"
- It will need a diet of meaty items, herbivore preparations, and flaked foods.
- Due to its aggressive behavior as an adult, it will do well with other moderately aggressive fish in a community tank and should be added last to avoid territorial conflicts
Ghost Goby (Fusigobius neophytus) -
- Minimum tank size = N/A
- Maximum size in aquarium approx. 2"
- Detritus eater and scavenger
Boxer Shrimp (Stenopus hispidus) -
- Minimum tank size = 30g
- Maximum size in aquarium approx. 3" (6" with feelers)
- It can destroy corals and anemones by nipping them open to feed on ingested food
- It may harass other smaller shrimp of different species
- It needs sufficient room to allow it to move without its long antennae touching neighboring corals or anemones
- It is an opportunist scavenger and will attack and eat small fish and inverts given the chance
Hope this helps people make an informed decision on whether to take on these fish and inverts. I personally would give the Boxfish and Cowfish a
very wide berth and wouldn't even consider the Mandarin unless the tank was 6mths+ old and full of live rock.