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FAQs about Cardinalfishes, Family Apogonidae, Compatibility 

Related Articles: Cardinalfishes

Related FAQs:  Cardinalfishes 1, Cardinalfishes 2, & FAQs on: Cardinal ID, Cardinal Behavior, Cardinal Selection, Cardinal Systems, Cardinal Feeding, Cardinal Disease, Cardinal Reproduction,  & Banggai Cardinals, Banggai ID, Banggai Behavior, Banggai Compatibility, Banggai Selection, Banggai Systems, Banggai Feeding, Banggai Disease, Banggai Reproduction,

Cardinal Fish Compatibility     5/13/14
<Big E!>
Do you think it is possible to mix different types of Cardinal Fish in reef display?
<Oh yes... have seen this done... and occurs in the wild>
I currently have 8 red spot cardinals(Apogon parvulus) and wanted to add a trio of yellow stripped cardinals (Ostorhinchus cyanosoma). Do you think this would work?
<If you have room... the bigger the better system-wise. BobF>

Orange lined Cardinalfish compatibility    4/7/12
Hey guys! I was wondering if Apogon cyanosoma (orange lined Cardinalfish) are compatible with small shrimp and crabs.
<Yes; just not very small shrimp, or largish crabs>
 I ask because I have a pair of Pterapogon kauderni in another tank and I'm aware of their propensity to eat small shrimp, but I haven't been able to find any information about A. cyanosoma eating them. I have a 29 gallon biocube with a Darwin Amphiprion ocellaris, Nemateleotris decora, spawning pair of Synchiropus splendidus, pair of Lysmata amboinensis, pair of Lybia tesselata, a pair of Periclimenes brevicarpalis and way too many corals to name. I would really like to get an A. cyanosoma but I'm concerned it may kill and eat my P. brevicarpalis and L. tesselata. Could you tell me your opinion on this?
<These should be fine. I would be/am more concerned re the Clownfish and small crustaceans; but it will likely be okay as well. Bob Fenner>

Pajama cardinal aggression    3/23/09
Greetings Crew!
Got a problem that I am not sure on how to proceed.
In my well established reef tank, one of my pajama cardinals has taken to beating up the other one.
<Mmm, does happen>
They have been in the same tank since I got them for well over 3 years ago. Never had any problems with them as they have been model citizens. Now the slightly smaller of the two is getting beat up by the other one. Took some time watching the tank to figure out who was the guilty party. His fins are about half of what they should be and he (I assume it is the male) has taken to hiding in corners or next to powerheads.
Starting not to look too healthy, but is still eating normally.
Tank info: 50 gal tall, plenty of LR. Other inhabitants are a mated pair of Perculas, a pair of blue-green chromis and a small Foxface.
<This last needs more room...>
Also a cleaner shrimp and an assortment of small inverts (snails etc..). Nothing new has been added for months.
Is this normal male-female aggression or do I have to think about breaking them up?
<Does... if you had a bigger system, at least a hundred gallons, I might suggest adding one or more of the same species... this is how they live in the wild... But there's not enough room here>
<Welcome. Bob Fenner>

R2: Stocking List/Introduction for 750 Gallon System -- 02/18/09 Eric, <<Hi Adam>> One reason I have been hesitant to add cardinals is because the cleaner and pistols I want to include. <<The species I listed should not pose much, if any, threat re>> I had the pair of Banggais on the list but wasn't completely set on the decision. I have 2 large skunk cleaners, one Alpheid, with plans of adding one more Alpheid and a fire shrimp to the big tank. <<I see no problems here re the Cardinals>> How well can the cardinals be trusted with larger sized cleaners and the goby guarded Alpheids? <<In my experience this has not been a problem with the smaller species I listed>> A friend of mine had bad luck with a pair of Banggais (the male was the culprit, female remained in the tank innocent), the male was caught with one of the smaller cleaners in its mouth after a long time of peaceful coexistence. <<Happens>> Cardinals occupy the shrimp eating niche in the wild don't they? <<Mmm, many of our aquarium fishes will devour shrimp of the right 'size' if/when encountered. The Cardinals are planktonic feeders primarily, watching for and plucking morsels from the water column, but will also feed on small crustaceans, worms, etc., when opportunity presents>> Any thoughts on this? <<I think either Cardinal species I recommended poses small risk to the ornamental shrimps (just don't drop the shrimp in to the tank like food when introducing new specimens), with the smaller Apogon leptacanthus posing the less of the two. Cheers, EricR>> 

Cardinal, Clown Aggression 1/26/09 I have had a blue tang, 2 false Perculas and a cardinal together for roughly 2 yrs. 6 months ago, I moved them to a 60gl tank. <The tang will need a much larger tank.> Over the past few weeks, my Perculas have began attacking my cardinal. To the point that he has half the fins before this started. Are there any thoughts on why this would start? <New tank, new territory, the clowns have decided there is no room for the cardinal.> Thoughts on how I can stop it? <Rearranging the tank decor may help, along with separating the fish for a week or two, but no guarantees.> I've already tried placing the Percs in a plastic container for a week, but they're back at it. <Not a good sign.> The cardinal spends all day in the corner of the tank, behind a rock. Thoughts? Thanks for your help Mike <Most likely these fish will need to be separated permanently.> <Chris>

Re: Lionfish problems, Apogon incomp.  1/19/09 Just thought you folks would like to know what I discovered. Bob suggested a tank divider which I did purchase and install. The fish were not at all happy but I had to determine what was causing the Lionfish's (body) areas of discoloration. It took about seven weeks before I noticed the body areas healing so Bob's theory of tank mates chewing on him looked correct. I removed the divider and they were all happier. That night though, I glanced at my tank and saw the Lion begin to do his nightly ritual of swimming back and forth, the length of the aquarium. The little Cardinal always stays at the back wall in the center of the tank but in the Lion's path. This little fish refuses to get out of the way of the Lion and sometimes (looks) like he's attempting to nip him. The culprit? Perhaps. He also follows the Lion on his swimming path. I never knew Cardinals were this aggressive. <Mmm, one can never tell as the saying goes... Being so nocturnal, seemingly passive, I also wonder> I keep monitoring and then decide if the Cardinal should find a new home. Thanks very much for the advice Bob. I would have bet anything you were going to tell me it was lateral line erosion or some other disease. I never would have guessed it was one of his tank mates. I guess I'll have to rig up a divider and see if it clears up. I'll let you know. Regards, Rob <Thank you for this valuable follow-up Rob. Bob Fenner>

Apogon leptacanthus--Aggression between School Members? ~ 01/11/09 Hi, folks. <<Greetings>> I was just wondering if you all could clear up something for me <<Will try>> ...I was talking earlier this evening to an employee at my LFS. He told me that in his experience, all Cardinalfish, even apparently placid schooling species like A. leptacanthus, will eventually pick each off in a tank setting (much the way that Anthias and sometimes Chromis will) until the school has dwindled down to the largest and strongest members. <<Hmm'¦ In 'my' experience, this is one of the few families of fishes where there seem to be a few species that 'do' get along in a group in most hobby-size systems. That said, there are always exceptions>> Have any of you observed this? <<With Anthiines and Chromis, yes'¦ But with 'some' species of Cardinalfishes, I have seen groups kept successfully. I think success with groups of Cardinalfishes (any fishes), aside from species selection, also has much to do with the size of the tank, how well the fish are fed (and making sure ALL get something to eat), and even the choices for tankmates>> I ask because I currently have a school of 9 or 10 Apogon leptacanthus in a 75-gallon reef tank, <<Ah'¦ A neat little fish'¦ And though not overly colorful, still quite attractive 'in person' and in a group setting. I have a dozen Sphaeramia nematoptera in a 375g reef display, and though they definitely have a pecking order, they are not as aggressive towards/with each other as the previously mentioned Anthiines and Chromis, nor have I experienced any mortalities>> and I've never observed even the slightest aggression between any of them. <<This species is considered one of the most peaceful of the Cardinalfishes>> I have lost a couple over the last six months, but they were in a system with a Stenopus shrimp and a (not the green "death star") brittlestar (both of which have since been removed), so I wonder if one of those could have been the culprit? <<Possibly'¦ Or maybe even old age>> The LFS employee said that he never observed any aggression between his Cardinalfish either, but that he lost one every few days, even though they had no obvious signs of illness, injury, parasites, etc. <<That he saw/identified'¦ Hard to say'¦>> Now, I'm thinking (hoping!) that maybe this was just attrition due to the fact that his fish were freshly imported and A. leptacanthus seem to be poor shippers and a little delicate before they settle into a new system. <<Poor handling may well have been the problem. Or maybe even stress from 'too aggressive' tankmates. But I can only guess>> Every source I've read (which, granted, isn't extensive for this species) has indicated that these fish do well--indeed, best--in schools, <<Agreed>> and in fact specifically mentions that they *won't* harass or bully each other the way that Banggais (for example) do conspecifics. <<Agreed again>> I've kept "pajama" Cardinalfish too, and they picked at and chased each other occasionally <<Yes>> in a way that I've simply never observed in my A. leptacanthus. On the other hand, this guy has about a decade of experience keeping all kinds of reef creatures and is usually a very reliable source of information... <<Mmm, but maybe his experience in this particular instance is limited to the one occurrence'¦ And in which he himself admits to not observing aggression, and seemingly having no real explanation for the fishes' demise>> Anyway, I'm hoping you all can clear this up for me. <<I don't know about clearing anything up'¦ But I do agree with 'your' take on A. leptacanthus>> Thanks for your time and assistance--I've always gotten good advice from you before and I so appreciate it! <<Is a pleasure to share. EricR>>

Cardinal compatibility, and a question about foods  11/30/08 Hello I recently purchased 3 orbiculate Cardinalfish, Sphaeramia orbicularis, from a local store. At the store in the same tank they had a pajama cardinal. I really liked the look of the two cardinal species together. I have heard that these cardinals are not as aggressive with conspecifics as Banggai cardinals. <This is assuredly so... both in the wild and captivity> Would I be able to mix the orbiculate cardinals with three pajama cardinals in a 75 gallon tank? <Likely so> I was also wondering how nutritious bloodworms are for saltwater. <Quite so> I have heard that they are higher in fat than other frozen foods. I have currently been feeding the cardinals as well as some gobie-esque fish (2 scissor tail Dartfish, 1 bar goby, 3 convict gobies) frozen bloodworms as a treat as they seem to really love them. In addition to this I have also been feeding krill, brine shrimp, mysis, daphnia, Cyclops, flake (TetraMarine Marine Flakes), pellets (Nutrafin Max Slow Sinking Morsels), raw table shrimp, silversides and a frozen food for marine angels. I generally feed two to three different foods per day. Is there anything you would recommend be added to the diet? <Mmm, no... and I'd like to put in my formal request to be reincarnated as a pet fish in your care> Thanks for your time Kevin <Thank you for sharing. Bob Fenner>

Re: Cardinal compatibility, and a question about foods  11/30/08 Thank you Bob for the quick reply. it's one of the things that makes this web site so great. <Ah, welcome my friend. My "central thread" here is that my and friends' efforts be accurate, significant and meaningful... including, of course, timely. Cheers, BobF>

Banggai eating up all the pods! - 4/12/04  Hello crew!  I do not have a problem, just an observation and I want to double check with one of you. Great!> I have had a Banggai for about 10 months. He is healthy and happy. Before I purchased him, I had a nice size population of pods. I really never gave much thought about it but now that I look back, I realize that my pod population has lessened. <Well, populations do go through growth gains and losses through a cycle. Predation also seems to cull quite a few out. Banggais will eat amphipods and copepods to supplement their diet for sure. What other potential predators do you have?> Could it be?! <Absolutely> Am I actually supplying him natural food? <Sure. For how long will be determined by a refugium (place for these creatures to grow without predation) or depending on how bug the tank is> Do Banggais eat pods? <Sure> I know they are nocturnal just like the pods. <Sort of> I had worried that he only ate Mysis (which is every fourth feeding) but he has always been the fattest booger in the tank. <They love Mysis and Cyclop-eeze> That's my guess anyway. Oh, and for those that think they are slow and boring, let me tell ya, when the Mysis hit the water, he swims circles around my blue tang and Foxface. <Yeah, they can hang in most cases> He looks like a silver bullet streaking across the tank. <What type of Mysis (brand) do you feed?> They are quite fast when they want to be. <I agree>  Anyway, take care guys and gals, <Thanks for the update. A valuable observation! ~Paul>  Jason

Pajama cardinal/elegance coral Hello again Bob, I hope you can save the day again'¦ The little pajama cardinal seems to have taken a liking to my elegance coral Always hovering.. picking at it, yet I do not see damage and the coral does not recoil..  Is the coral safe?, should I be concerned? <These associate in the wild... no problems... the cardinals likely receive some protection from predation... Catalaphyllia sting like no tomorrow...> The little sweetie would be impossible to catch and a shotgun to a 20g nano might prove destructive'¦.don't you agree? <A twenty gallon system is too dangerously small for this Euphylliid> Thanks for being there. Ellen <Bob Fenner>

Cardinal swallows shrimp, Legs still sticking out. 12-06-05 Hello Crew, <Hello> A pajama cardinal ate our skunk cleaner shrimp last night after it molted. The shrimp doesn't fit in the cardinal's stomach as legs and antenna are sticking out of the mouth. <I must say this is a first.> My wife called me with this info at work, so I haven't seen it yet. Will the fish die, too? <The fish should be able to evacuate the shrimp on its own. If it does not do so, or looks to be laboring then you may need to help it out.> Anything that can be done to save it? My wife saw the empty molt, so she's sure it's the actual shrimp that got eaten after it molted. The shrimp is full grown and almost as long as the cardinal and I never thought it would try to eat it. <They will try anything that will try to eat anything that will fit in their mouth. Travis> 

Re: Cardinal swallows shrimp, Legs still sticking out. 12-06-05 Thanks for the reply, but it turns out my panic was unwarranted. <That is good. Always better to waste worry than to be right for worrying.> Over the course of the day, the legs and antennae slowly disappeared into the fish until they were gone a few hours after my initial mail... and it grabbed the largest piece of food at dinner time when I fed the tank. <Sea pigs.> I assumed the shrimp was too large to fit in the cardinal's mouth. It seems I was wrong.  <It does seem so...> Pajama cardinals won't be going into my next reef.  I'm looking at threadfins to fill the niche instead, in hopes that they won't eat my beloved Lysmata shrimps. <You will greatly enjoy the thread fins. They can also be kept in schools which is nice. Travis> Thanks, Ben 

Mixing Cardinals As always you guys rule.  <Thank you> I have 3 PJs whom I love, living in my 75. One has been with me for years and years, she's my "other woman." It's her eyes :). (I know its a she because one of the new guys had to carry her eggs quite a few times). Anyways, I have some space for a few more fish, not many but like maybe 2. I always wanted Banggais, and I am trying to find out if 3 PJs and 2 Banggais would be happy in my tank. My utmost concern is for the PJs with the usual irrational exuberance for new fish that is shared by most people with my affliction as a secondary issue. The only other top fish is a royal Gramma and a tomato clown that has a anemone. Lots of rockwork. Thanks again and again for all the information over the years. <James, definitely go with the Banggais. The tomato is not a good choice to mix with cardinals. James (Salty Dog)> 

Seahorses and Cardinals    9/22/06 Hi, (to whom gets to answer my questions today:) <That would be me, Leslie> I have a 30 gallon hex tank with 2 captive bred seahorses (I'm not sure what kind they are, but they are about 4" long) a yellow Watchman Goby and a Cleaner Shrimp. For filtration I have a Rena 3 canister filter with the flow turned down so the seahorses don't go flying around the tank. The whole setup has been running and happy for over a year now and the question that I have is.....would it be okay to add 2 or 3 PJ Cardinals to this system? Some websites say yes others say no and on WWM I have not been able to find an answer. <Well they would do fine with seahorses and do well in small groups. They do however get to be close to 4 inches long and are wide dorso-ventrally. IMO a 30g hex is to small and does not have enough horizontal swimming space. Instead you might want to consider a captive bred Pseudochromis fridmani (Orchid Dottyback); an Assessor either the A. flavissimus (Yellow Assessor) or the A. macneilli (Blue Assessor); a Firefish either the N. decora (Purple Firefish) or the N. magnifica (Fire Goby); or a Ecsenius midas (Midas Blenny)> Thank you for your time and expertise, Diana <You're most welcome, Leslie>

New aggression in Cardinalfish   1/23/07 Hi, I have a 75 gal FOWLR tank that we just recently got back together after a nasty bout with Ich - lost many of my fish... 3 blue green chromis, 1 Banggai cardinal, 2 yellow tail blue damsels and 1 Foxface rabbit survived  - I broke down the tank, put them into a quarantine tank for 45 days - copper treatment - and then put them back into the big tank which also has 3 cleaner shrimp, 3 peppermint shrimp, 2 oysters, a featherduster and a few hermit crabs and snails ... they were all fine with each other before and also in the q tank but when they went back into the big tank the damsels attacked and almost killed the cardinal - all his fins were gone and he was bleeding... a peppermint shrimp had dragged him under the rocks for a snack - he shot out of the rocks and I scooped him out and ran him into the q tank which was still operating - it is an absolute miracle that he survived... he didn't eat for over a week and then I tried feeding him live feeder shrimp ... It took over a month but he has grown all his fins back, <Good. This is a quick recovery> is eating his regular diet (frozen and pellet) and I moved him back to the main  tank , caught the 2 damsels (with the help of a trap) and returned them to my LFS (very nice people there),   I decided to add just 2 more special fish to the tank and to keep it that way for a while - I bought a Majestic angel (3 1/2 inches) <Yikes... a touchy species, sub-genus, and needs much more room... see WWM re> and a Lined Fairy Wrasse (4 inches) - both absolutely beautiful fish.  I had them in the q tank for over 3 weeks and moved them into the main tank .... here's the issue .... after 3 weeks, the Cardinalfish has begun to harass the other fish ... not the wrasse or the angel but he is terrorizing the rabbitfish!  The poor guy is raising his spines constantly and trying to hide all the time ... The cardinal is also going after the chromis ... I know that I changed the dynamic in the tank adding the last 2 fish ...  I hate to give up the Cardinalfish ... he is such a special guy to have survived his ordeal... <Perhaps another tank?> but I just noticed a few tiny white spots on the wrasse's fin ... please advise.... should I just see if things settle back down and keep an eye on them ?... do they usually work this out in the tank, there are plenty of places to hide and swim ? <Mmm, not in a 75 gallon box there isn't> - they seem to do better if I keep them well fed (3-4 times a day) but I'm afraid to overfeed-   Yikes!   I REALLY don't want to deal with another Ich break out . Thanks, Beverly A <I would remove the cardinal... just observe the rest. Do read on WWM re. Bob Fenner>

Compatibility - 10/13/06 Do you think two Nemateleotris magnifica and one Sphaeramia nematoptera can be kept together? <<Indeed...should not be a problem>> Thank you so much for your advice. <<Quite welcome, EricR>>

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