This is meant not to warn you off certain species, but to advise you of some of the problems in keeping them. Everybody may have their own list. But these are some I have experience with. Your mileage may vary by tank shape, tank design, oxygenation, and personal preference.
Top of the list: dragonets. Mandarin 'gobies' ---they aren't gobies---and scooter 'blennies'---they aren't blennies.
Dragonets are copepod eaters, hundreds and hundreds every day: requires at least a 50 gallon tank with no competition for copepods supported by a 20 gallon year or more old fuge producing pods like mad.
Dartfish firefish, blue gudgeons, scissortails, barred dartfish: very skinny and can disappear right into the slots of many downflow boxes. They also jump amazingly high and seem to find the only gap in the jump screen.
Damsels are often brilliant blue or a white-black combo, and grow up to 4" (except the garibaldi, which grows huge!) and in too small a tank will fight other fish. Give them a 100 gallon and you can keep a number of species of damsel together. In a 100 they also tend to ignore non-damsels, or sometimes swim with them for a space. I have a 4.5" dascyllus who pals with a matted filefish. Do also check out the adult coloration. Some turn into grey or dark fish as they get older. They come in two common types, the chrysipteras, and the dascyllus. Chrysipteras are the long-bodied quieter sort and often max at 3"; the dascyllus species grows disc-shaped and fat and tend to 'boss' a tank. Given enough room, they won't bite, just chase. If you think dascyllus, think 'maroon clown' and that might explain everything.---One side note: dascyllus and chromis do not get along nicely.
Chromis are a smallish damsel-style fish that will tend to school somewhat if under threat. They kill each other for sleeping spaces at night. If you have too many for the space, they will reduce their number, picking off the weakest nightly. They are also very prone to uronema: red spots and a cottony growth are both signs of disease that can affect other fish.
Rabbitfish grow up to 10" and have a poisonous dorsal spine that can kill other fish. They are easily spooked, and if kept in too small a tank for their growing size, they can defend themselves. They also tend to plaster themselves under rockwork when the owner is working in the tank, and if hand meets fin, a very nasty wound can happen. The venom is similar in effect to a fiddleback spider bite, at least from what I've seen: necrosing tissue. On another fish, tends to be a telltale red spot. And I know of one case where the rascal, fine for a couple of years, took to eating lps corals.
Dottybacks are very inclined to hide in rocks and attack other fish. I had this behavior in a hundred gallon tank, and had to disassemble the rockwork to get the fellow out. Pretty, but pugnacious, and smart: you get one try per method of catching him. After that, he's on to you and you have to change methods. If you love the shape and color and want a alternative, consider the yellow and fuschia royal gramma (one dottyback looks a lot like him), who is shy and not nippy. The Midas blenny is a similar shape and color to some dottybacks.
Angels large ones aren't reef safe. Dwarf species may be safe with certain corals, but the appetite may develop over time. Caution.
Tangs many species grow quite large, and get there fast. Plus some types need space to make long swimming runs, for their health, and are best in a 'long' rather than 'deep' tank. Always, always look up the adult size of the tang species you are considering. There is, in SETTING UP, a list of recommended tank sizes for this species, which is about the largest fish we keep. Be advised: "Dory" can approach a foot in length and get fat besides. They require 'green' food, but appreciate a little meat in the diet.
Dragon goby moves sand all over and can endanger sand-sitting corals. Yellow watchman goby, fyi, moves far, far less, and still does a nice job.
Very tiny gobies are sold as adults and can go right through the drainage slits. Look at your own situation with that.
Anemones have lighting requirements, water movement requirements, and water chemistry requirements. If one dies in your tank, it melts in a welter of loose stinging cells and a horrific smell. Always have carbon on hand if you have a nem. They go where they want, not where you place them, and only a skilled handler should attempt to move one. They are also good at finding their way into powerhead intakes and fatally injuring themselves. Lovely, but become a water expert before you adopt one. Having one in a tank with coral is a risk.
blennies require a certain amount of green food, imperatively. They're also prone to fight if crowded by another of the same kind. The tailspot and starry are compatible: I have kept them. But be a little cautious about too much similarity in looks. And unlikely as it seems, they will jump, and the little ones can go through the slits.
Clowns come in small and relatively peaceful and large and not so peaceful---just like damsels, which they actually are. Some damsels will 'host' in a nem; clowns in general will---but not just any nem. You have to match anemone species to clown species, and your lighting has to be adequate for the type of anemone. If your tank doesn't offer a nem (and a novice owner should not until the owner is a water-quality expert), they will host in toadstool leathers, hammer coral, bubble coral, clams. They are prone to ich and brook. They are often captive-bred. If you have a small tank, get a small species. BUT ---a mated pair of anything is a whole different sort of fish. I kept Clarkiis in a 100 gallon: they have teeth, they will bite the hand that feeds them and draw blood, and they and their nem took 50 gallons all to themselves. It was a damsel tank, and they terrorized my damsels---no kidding: a blue velvet damsel, one of the nippier sorts, ran in terror from either of those fish. Clownfish of the smaller, more peaceful sorts can be a good answer for a 30 gallon, and they do get quite interactive with anybody who approaches the tank.
Top of the list: dragonets. Mandarin 'gobies' ---they aren't gobies---and scooter 'blennies'---they aren't blennies.
Dragonets are copepod eaters, hundreds and hundreds every day: requires at least a 50 gallon tank with no competition for copepods supported by a 20 gallon year or more old fuge producing pods like mad.
Dartfish firefish, blue gudgeons, scissortails, barred dartfish: very skinny and can disappear right into the slots of many downflow boxes. They also jump amazingly high and seem to find the only gap in the jump screen.
Damsels are often brilliant blue or a white-black combo, and grow up to 4" (except the garibaldi, which grows huge!) and in too small a tank will fight other fish. Give them a 100 gallon and you can keep a number of species of damsel together. In a 100 they also tend to ignore non-damsels, or sometimes swim with them for a space. I have a 4.5" dascyllus who pals with a matted filefish. Do also check out the adult coloration. Some turn into grey or dark fish as they get older. They come in two common types, the chrysipteras, and the dascyllus. Chrysipteras are the long-bodied quieter sort and often max at 3"; the dascyllus species grows disc-shaped and fat and tend to 'boss' a tank. Given enough room, they won't bite, just chase. If you think dascyllus, think 'maroon clown' and that might explain everything.---One side note: dascyllus and chromis do not get along nicely.
Chromis are a smallish damsel-style fish that will tend to school somewhat if under threat. They kill each other for sleeping spaces at night. If you have too many for the space, they will reduce their number, picking off the weakest nightly. They are also very prone to uronema: red spots and a cottony growth are both signs of disease that can affect other fish.
Rabbitfish grow up to 10" and have a poisonous dorsal spine that can kill other fish. They are easily spooked, and if kept in too small a tank for their growing size, they can defend themselves. They also tend to plaster themselves under rockwork when the owner is working in the tank, and if hand meets fin, a very nasty wound can happen. The venom is similar in effect to a fiddleback spider bite, at least from what I've seen: necrosing tissue. On another fish, tends to be a telltale red spot. And I know of one case where the rascal, fine for a couple of years, took to eating lps corals.
Dottybacks are very inclined to hide in rocks and attack other fish. I had this behavior in a hundred gallon tank, and had to disassemble the rockwork to get the fellow out. Pretty, but pugnacious, and smart: you get one try per method of catching him. After that, he's on to you and you have to change methods. If you love the shape and color and want a alternative, consider the yellow and fuschia royal gramma (one dottyback looks a lot like him), who is shy and not nippy. The Midas blenny is a similar shape and color to some dottybacks.
Angels large ones aren't reef safe. Dwarf species may be safe with certain corals, but the appetite may develop over time. Caution.
Tangs many species grow quite large, and get there fast. Plus some types need space to make long swimming runs, for their health, and are best in a 'long' rather than 'deep' tank. Always, always look up the adult size of the tang species you are considering. There is, in SETTING UP, a list of recommended tank sizes for this species, which is about the largest fish we keep. Be advised: "Dory" can approach a foot in length and get fat besides. They require 'green' food, but appreciate a little meat in the diet.
Dragon goby moves sand all over and can endanger sand-sitting corals. Yellow watchman goby, fyi, moves far, far less, and still does a nice job.
Very tiny gobies are sold as adults and can go right through the drainage slits. Look at your own situation with that.
Anemones have lighting requirements, water movement requirements, and water chemistry requirements. If one dies in your tank, it melts in a welter of loose stinging cells and a horrific smell. Always have carbon on hand if you have a nem. They go where they want, not where you place them, and only a skilled handler should attempt to move one. They are also good at finding their way into powerhead intakes and fatally injuring themselves. Lovely, but become a water expert before you adopt one. Having one in a tank with coral is a risk.
blennies require a certain amount of green food, imperatively. They're also prone to fight if crowded by another of the same kind. The tailspot and starry are compatible: I have kept them. But be a little cautious about too much similarity in looks. And unlikely as it seems, they will jump, and the little ones can go through the slits.
Clowns come in small and relatively peaceful and large and not so peaceful---just like damsels, which they actually are. Some damsels will 'host' in a nem; clowns in general will---but not just any nem. You have to match anemone species to clown species, and your lighting has to be adequate for the type of anemone. If your tank doesn't offer a nem (and a novice owner should not until the owner is a water-quality expert), they will host in toadstool leathers, hammer coral, bubble coral, clams. They are prone to ich and brook. They are often captive-bred. If you have a small tank, get a small species. BUT ---a mated pair of anything is a whole different sort of fish. I kept Clarkiis in a 100 gallon: they have teeth, they will bite the hand that feeds them and draw blood, and they and their nem took 50 gallons all to themselves. It was a damsel tank, and they terrorized my damsels---no kidding: a blue velvet damsel, one of the nippier sorts, ran in terror from either of those fish. Clownfish of the smaller, more peaceful sorts can be a good answer for a 30 gallon, and they do get quite interactive with anybody who approaches the tank.
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