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FAQs on Silver Dollars Behavior

Related Articles: Serrasalmine Fishes, Piranhas, Characoids/Tetras & Relatives

FAQs on: Silver Dollars (Metynnis, Mylossoma, Myleus...spp.) 1, Silver Dollars 2,
FAQs on: Silver Dollar Identification, Silver Dollar Compatibility, Silver Dollar Stocking/Selection, Silver Dollar Systems, Silver Dollar Feeding, Silver Dollar Health, Silver Dollar Reproduction, Related FAQs:  Serrasalmine Fishes, PiranhasPacus,

biting Myloplus rubripinnis     11/25/13
I searched for two hours for info re: my problem. You are my last hope.
<Oh? Oh!>
I have a pair of red hooks (Myloplus rubripinnis) in a 55 gallon tank
<Mmm, really need more specimens... like most Serrasalmines, these "silver dollars", live in schools; and much more room for them>

 with 3 African Clawed Frogs,
<Mmm, must be hard to feed here>
1 Convict, 1 plecostomus, and 1 apple snail.
The larger red hook has bitten the smaller red hook on both sides with vigor. The smaller red hook is missing a lot of skin.
<Again; to re-emphasize... need to be kept in a group (dilutes aggression) and bigger world (ditto)>
Is there anything I might use to treat these injuries? 
<Mostly just moving them to a larger system>
Could I add some kind of sedative to the water to calm the large red hook?
<Mmm, no; not really>
Do they make Ritalin for fish?  Ha!
Should I get two more red hooks?
<Three would be better; but only in a hundred plus gallons>
The large red hook is aggressive with everyone in the tank.
I am feeding everybody red worms.
Ph and temp. are normal.
Thank you for any help you might offer.
<I do hope yours recovers... Have you searched, read what is archived on WWM re these fishes? Bob Fenner>
Re: biting Myloplus rubripinnis      11/25/13
Thank you, Bob.
<Welcome Sandran>

Silver Dollars chasing each-other   12/29/12
I have 5 Silver Dollars in a 7ft tank with two Oscars, one Jack Dempsey, one Featherfin Catfish and one Shark fin Catfish. I know it sounds like a lot in one tank but their all pretty peaceful, the Oscars do fight from time to time, which is normal. The only problem is my Silver Dollars chase each-other like there's nothing else to eat.
<What they do>
 Also their not vegetarians they love bloodworms and crickets.
<Ah yes... are part of the same subfamily as the Piranhas (Serrasalminae); are omnivorous>
Thank you
<As you state; this size, shaped system should be fine for all you list... as long as the Oscars aren't breeding! Bob Fenner>
Re: Silver Dollars chasing each-other   12/30/12

Thank you for answering so quickly. My Silver Dollars look like their fighting for territory, also they have small bite marks on their side but they don't seem to be biting each-other.
<Mmm, well they do... as you state, territoriality mostly... not a problem as long as one doesn't get singled out, starved>
Another quick question, I have no idea what sex my Oscars are, I read that it's near to impossible to identify but if you have any tips so I could get some sort of clue, it would be great.
Thank you
<See WWM re... use the search tool, indices... Oscar Reproduction FAQs.
Re Silver Dollars chasing each-other    12/31/12

 My Silver Dollars look like their fighting for territory, also they have small bite marks on their side but
> they don't seem to be biting each-other.
> <Mmm, well they do... as you state, territoriality mostly... not a problem
> as long as one doesn't get singled out, starved>
> Another quick question, I have no idea what sex my Oscars are, I read that
> it's near to impossible to identify but if you have any tips so I could get
> some sort of clue, it would be great.
> Thank you
> <See WWM re... use the search tool, indices... Oscar Reproduction FAQs.  BobF>
I  Searched but nothing. I still have a problem with Silver Dollars?
<<See prev. corr.... B>>

Will different silver dollar species school together? 7/28/10
Hi Crew - I have 4 spotted Metynnis (spotted silver dollars) and wanted to add a couple of normal silver dollars to add variety. Will they school together?
<They'll get along, but there's no guarantee they'll school together. A good rule of thumb is to keep no fewer than five of any one Silver Dollar species. Any fewer and there's always a risk of in-fighting and dominance issues. Of course, your own mileage may vary, and the size of the tank makes a huge difference. Cheers, Neale.>

Molly & Dollar... beh., sys.    1/18/10
I have quite a strange situation going on and I'm honestly not too sure how to go about fixing it.
<Do start by reading here:
Mollies are very misunderstood, and a depressing proportion of them end up dead prematurely.>
Recently, my boyfriend and I purchased a balloon molly as well as a silver dollar. Just the other day we also purchased a 29 gallon tank, so in a week or so we will be getting a few more of each.. the thing is, our molly seems to adore the dollar. Whether or not it's a sign of aggression, I'm honestly not sure.
<It is aggression. I've seen this same thing before with Sailfin Mollies and Australian Rainbowfish.>
Basically what is happening is that our molly is always stuck right next to our dollar. Usually that's all he does, he just sits next to the dollar, occasionally he may kind of rub up against the dollars side.. sometimes though the molly sort of nips at the dollar's side and the dollar may take off suddenly but usually slows down and the molly's right next to his side again.. now the dollar doesn't seem to mind the molly all that much- usually if the molly goes off to pick at some food or whatever, the dollar is right behind him... I've read before that sometimes mollies will nip at
other fish but not in a harmful manner. I'm not sure if this is true but I'm just beginning to wonder how much stress this is causing the dollar, if any at all... I have searched the web and cannot find this same situation happening to anybody else. As I said, in a week or so we will be moving them to a bigger aquarium, I'm just wondering what might happen if we get a few of each.. we were thinking of at least one other dollar, maybe two, but reading this site, it looks as if I'll need more...? Please tell me what you can! As I said, the molly really doesn't seem to cause any harm at all to the dollar- he seems to absolutely adore him.. and to be honest- the dollar doesn't really seem to mind the molly all that much either.. I attached two photos, both of them have each fish together.. the second one is a little tougher to find the dollar but if you look at where the molly's lips are....... I apologize for the lack of quality, I lost my camera so I had to use my phone to take the pictures.. Anyway, please let me know if this is causing stress on either fish or if it will once we purchase a few more! Thanks so much .
<Now, there are two issues here. Firstly, Silver Dollars are schooling fish. They need to be in groups of 5 or more specimens. They also get very big. VERY BIG. So unless you have a 55 gallon tank in the near future, don't keep them. These are big, nervous, herbivorous (eats plants) fish not suited to the average community tank. Now, as for the Molly. Male Mollies fight for dominance by showing off. Essentially they display their size and fins to one another, and the one with the biggest fins wins. What happens if a male Molly is in "solitary" confinement is that he looks for females (finds none) and looks for rival males (finds none). Then he looks for anything that *might* be a Molly. My guess here is that arch-backed fish -- like Australian Rainbows and Silver Dollars -- resemble the silhouette of a male Molly with erect fins. In other words, your Molly thinks the Silver Dollar is another male Molly threatening him. There's no resolution here -- the Silver Dollar can't change his shape -- the male Molly neither beats the Silver Dollar nor gets the Silver Dollar to back down. So the rivalry goes on and on. The two species are not really compatible, so I don't see any point trying to get them to live together. Mollies need very warm, very
hard, basic water, ideally slightly brackish; Silver Dollars want middling temperature, soft, acidic water. Put each in their own aquarium suited to their needs, and your problem goes away. Simple as that. Cheers, Neale.> 

Red Hooked Metynnis   6/8/06 I have 3 large red hooked Metynnis.  The old guy or girl has been with me about 20 years. <How nice! Myleus are faves of mine> I feed them a diet of green beans, bananas, lettuce and  Hikari Cichlid Gold medium pellets.  I know this is a long time for a fish to live but just how long have these type of fish been known to live.  If you have time please give a response to me question.   Thanks so much  Jean Smith <I do believe there are some western European public aquariums that have had this species for more than thirty years. Bob Fenner>
Re: Red Hooked Metynnis   6/9/06
Thanks so  much for your reply.  I have mine in a 55 gal tank.  As I said I have the old one, and one that is about l0 years old and a juvenile that I have had about 5 years.  The old ones hook has lost some of the red and it seems to me that his red color has faded some.  I keep hoping that they might spawn. <Would likely need more room...> Also I have two small ones that I bought last year.  They do have big teeth  The two older ones have brown and black markings on them but the young one is still silver.  They are kind of crazy sometimes running into the tank and hurting their noses. <Mmm, again... need bigger quarters>   I just love them!  Again thanks for your reply.   Jean <Thank you for sharing. Bob Fenner>

hi. <Hello!> my oldest silver dollar has gone mad! - 6/7/07 <Oh dear.> he swims frantically around our tank & has hurt himself badly <Odd. Usually, this means the fish is unhappy for some reason. Can be water quality, but other factors to consider are: Noises (such as loud TVs or doors banging). Aggressive tankmates. Fin-nippers.> he has taken off his lips & fore head <Not sure what you mean by this. Is he damaged? If so, treat with anti-Finrot/anti-fungus medication to stop things becoming septic.> he does it at least twice a day <Try and establish if there is a routine. Are there children banging around the house when this happens? Characins are very sensitive to vibrations and sound. These are open water fish, and their response to alarm is to swim rapidly away from danger. In the confines of an aquarium, this can cause problems.> what's wrong with him? <No idea. Does he have friends of his own species? Silver dollars are very sociable, and won't really settled down if kept alone. A group of 6 or more is best.> our tank is huge & all checks are fine <Define "huge". At the very least, check there is plenty of swimming space and strong water current.> what do we do? <Not sure. How many silver dollars? What are the tankmates? How big is the aquarium?> thanks Donna <Cheers, Neale>
Re: silver dollar has gone mad! - 6/7/07
We have 3 silver dollars. His original friends died of old age. His new friends are only about 6 months old (had them about 3) but this behavior is new only about 2 weeks that he been acting weird, he took to the new babies straight away & hangs around with them all the time. <Very good.> Our tank is a huge corner one & we have a few female guppies & black & red shark & 2 Plecs. They have all lived happy for ages. The Water is clean, with filter & pump. He is about 7-9 years old & I have noticed him 'jump' before when I turned the Hoover on but in the past 2 weeks he has started dashing around our tank for no reason, he has hurt himself now. <Very odd indeed. He's a fair age though, so you've obviously been looking after him pretty well.> all the skin is missing from his lips & forehead. we are worried now & we don't know whether it is better to put him out of his misery. he's like one of the family though, we've had him years. <If he's otherwise fine, schooling with his pals and eating properly, then I personally wouldn't destroy him. I'd treat the tank with anti-Finrot/anti-fungus so that his skin heals properly. You could also add some Melafix as well. Give things a few weeks to see if he settles down. You might want to remove anything rough and spiky in the aquarium, just to make sure he can't damage himself further. You could also add some cheap floating plants, such as hornwort or Canadian pondweed, to see if the extra shade helps him settle down. A lot of fish enjoy floating plants. If things still don't improve in 3-4 weeks, then maybe then you might need to destroy him.> please help us <Cheers, Neale>

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