In general, a lot of things ride in on live rock, and in general, you want almost all of them. I set up with live rock and counted 52 separate species that came in with it. Worms, snails, copepods, amphipods, sponges, even bits of coral, algaes, etc...
The bad: pretty well limited to 1) fireworms, not to be confused with good bristleworms. They don't look alike. Look up hermodice carunculata on the internet. That's one bad guy.
2) eunice worms. This guy could live fine in your sump, but not in your tank. Look up eunicid worm. The tentacles are a dead giveaway.
3) crabs of most sorts. Little microhermits are good: hairy crabs are not. Nor are crabs in general that have distinctive large claws. Also do not be conned into buying a sally lightfoot or arrow crab. Interesting in your sump, but not for a reef.
4) shrimp: in general, things that go click and bang! in your tank late at night are predators, either pistol shrimp or mantis. They're fishkillers. I'm not personally keen on shrimp-goby pairs, either, after my tiger shrimp grew up and killed his goby partner plus several other fish before I took my tank apart to extract the fellow.
5) flatworms---some kinds are a problem, some less so. Many have a V taken out of the tail. THey range from tiny to monster. They're mostly a problem because they get so prolific so fast.
6) aiptasia or majano anemones --- never grow above an inch in size, though they are stretchy. They're brown, don't get color. Peppermint shrimp, if they take to eating them while the shrimp are juveniles, will assure you never have any problem with them. The trick to getting shrimp to eat them is buying about five juvie shrimp---out of the five, usually one will take to them. I've had rare setups where my five were ALL duds. But the next five would produce ravenous aiptasia-eaters. I like the little nems in the sump fuge: they're not bad citizens down there. In the tank, they can sting corals and get pushy, but honestly, I've raised corals for many years and never found them much real problem. If you overfeed your tank, you could see them multiply, but if you have a big bloom of ANY creature, figure you MAY be overfeeding your tank. Cut back, for starters.
Those are the chief problems, save one: ROOTED algaes. If it has roots and grows in the rock, and especially if it's caulerpa, get that rock out, and if it's the whole batch, that's a serious problem in any tank under 100 gallons: why? Because the only fish that can eat caulerpa (the onespot rabbit) is equipped with a poison spike and can turn killer of other fishes in a tank under 100 gallons. The other fish that will tackle algaes is the tang---and they also are a 100 gallon fish.
I advise against letting caulerpa exist in your sump, because it reproduces by spores and by fragments. It's far worse than hair or bubble algae, and is illegal in California for good reason.
Hope that's some help.
The bad: pretty well limited to 1) fireworms, not to be confused with good bristleworms. They don't look alike. Look up hermodice carunculata on the internet. That's one bad guy.
2) eunice worms. This guy could live fine in your sump, but not in your tank. Look up eunicid worm. The tentacles are a dead giveaway.
3) crabs of most sorts. Little microhermits are good: hairy crabs are not. Nor are crabs in general that have distinctive large claws. Also do not be conned into buying a sally lightfoot or arrow crab. Interesting in your sump, but not for a reef.
4) shrimp: in general, things that go click and bang! in your tank late at night are predators, either pistol shrimp or mantis. They're fishkillers. I'm not personally keen on shrimp-goby pairs, either, after my tiger shrimp grew up and killed his goby partner plus several other fish before I took my tank apart to extract the fellow.
5) flatworms---some kinds are a problem, some less so. Many have a V taken out of the tail. THey range from tiny to monster. They're mostly a problem because they get so prolific so fast.
6) aiptasia or majano anemones --- never grow above an inch in size, though they are stretchy. They're brown, don't get color. Peppermint shrimp, if they take to eating them while the shrimp are juveniles, will assure you never have any problem with them. The trick to getting shrimp to eat them is buying about five juvie shrimp---out of the five, usually one will take to them. I've had rare setups where my five were ALL duds. But the next five would produce ravenous aiptasia-eaters. I like the little nems in the sump fuge: they're not bad citizens down there. In the tank, they can sting corals and get pushy, but honestly, I've raised corals for many years and never found them much real problem. If you overfeed your tank, you could see them multiply, but if you have a big bloom of ANY creature, figure you MAY be overfeeding your tank. Cut back, for starters.
Those are the chief problems, save one: ROOTED algaes. If it has roots and grows in the rock, and especially if it's caulerpa, get that rock out, and if it's the whole batch, that's a serious problem in any tank under 100 gallons: why? Because the only fish that can eat caulerpa (the onespot rabbit) is equipped with a poison spike and can turn killer of other fishes in a tank under 100 gallons. The other fish that will tackle algaes is the tang---and they also are a 100 gallon fish.
I advise against letting caulerpa exist in your sump, because it reproduces by spores and by fragments. It's far worse than hair or bubble algae, and is illegal in California for good reason.
Hope that's some help.
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