Leaf Scorpionfish
The leaf scorpionfish is highly variable in color. When the juveniles settle out of the plankton they are nearly transparent. As they grow, they often take on the color of their surroundings. The overall color can be black, maroon, red, pink, brown, tan, dirty yellow, bright yellow or white, with dark or light mottling. Some individuals can be multicolored. For example, I have seen a pair of bicolored specimens from the Fijian Islands that were orangish on the belly and flanks with a bright yellow back and dorsal fin. This fish can undergo radical color shifts over long periods of time. For example, a pair of dirty yellow specimens at one dive site changed to white over several months time. The coloration can also change slightly if they move from a light to darker background, or vice-versa. Microalgae sometimes grows on their skin, which can also alter their color. This plant material is sloughed off along with the cuticle (outer layer of skin) when the leaf scorpionfish “sheds.”
The leaf scorpionfish is a patient predator. It relies on its amazing camouflage to ambush unsuspecting prey. While food habit studies have not been carried out on this species, it is assumed that they eat small crustaceans and fishes. I have often seen them surrounded by shoals of small cardinalfishes or sweepers. I imagine that the cryptic scorpionfish occasionally inhales one of these prey fish. It can ingest its food so quickly (by rapidly increasing the volume of its gill and mouth chambers when it throws its jaws open), that members of the shoal probably don’t even recognize the leaf scorpionfish as a threat. Food consumption tends to be rather low in the scorpionfishes – say, one or two prey items per day.
The first of these is feeding. If you have ready access to live feeder animals, either shrimp of live-bearing fish, than it should not be a problem. Leaf scorpionfish rarely turn down moving prey that is of the right size. I suggest you raise mollies or guppies in seawater. Feed these feeder fish a highly nutritious food, like frozen cyclops, mysid shrimp, or a protein/pigment-rich flake food. You should give the feeder fish/shrimp a good meal a couple of hours before you present them to your T. triacanthus (this is referred to as gut-packing). One thing to consider is that the leaf scorpionfish has a smaller mouth, relative to its body size, than many of their scorpionfish relatives – therefore, you need to select appropriate sized food items. Hepatic lipidosis, or fatty degeneration of the liver, has been reported in a scorpionfishes. This condition can causes liver failure, which leads to suppression of the immune system, hemorrhaging and anemia. Lipidosis is best avoided by giving your scorpionfish as varied a diet as possible and by not overfeeding.
The second challenge involves selecting “neighbors.” There are a couple things you need to take into account. First of all, avoid bold, pugnacious feeders that will snap-up the live food you add to the tank before the ambush-inclined leaf scorpionfish gets a chance to get its fill. If you do keep it with food competitors, you may have to corral the hungry leaf scorpion in a portion of the aquarium with a tank divider and feed it on its own. It is also possible to train a leaf scorpionfish to take live feeders from a net.  Place the food item in a net and slowly move it towards the predator. The leaf scorpionfish will gradually learn to jump into the net to capture live food.   

The second thing to consider is if a potential tankmate will harm your T. triacanthus. Some territorial species, like larger dottybacks and damsels, may attempt to drive a leaf scorpionfish from their domain. If the aquarium is small enough and it occurs incessantly, the scorpionfish may become stressed and refuse to eat. Some fish species, especially those the nibble on encrusting invertebrates, might also pick at the integument of the leaf scorpionfish. This often happens because the scorpion looks so much like the substrate these fishes normally graze from. As mentioned above, algae can also grow on the leaf scorpionfish’s skin which can elicit nipping by herbivores (e.g., pygmy angels, tangs, rabbitfishes). That is why, it is often easier to keep leaf scorpionfishes on their own, rather than with other fish species.