Silver Dollars Selection
Related Articles: Serrasalmine Fishes, Piranhas, Characoids/Tetras &
FAQs on: Silver Dollars (Metynnis, Mylossoma,
Myleus...spp.) 1, Silver Dollars
Silver Dollar Feeding,
Silver Dollar Health,
Silver Dollar Reproduction, Related
biting Myloplus rubripinnis 11/25/13
I searched for two hours for info re: my problem. You are my last hope.
I have a pair of red hooks (Myloplus rubripinnis) in a 55 gallon
<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
<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
Thank you, Bob.
Stocking a 55 gallon tank, FW
Thank you for all the wonderful things you do, I love your website.
I just acquired a 55 gallon tank and would like advice on how to stock
it, so I don't make the wrong choice and end up with unhappy fish.
I have heard that silver dollars are a stretch in a 55
gallon, but I would love to have them.
<The problems with Silver Dollars are two-fold. Firstly, they do get
rather big, typically 12 cm/5 inches, and secondly, you do need to keep
a group of six or more because they're social fish with the
potential to become aggressive or nervous when kept in insufficient
numbers. On top of these issues, they're both predatory and
pronounced plant-eaters, so they're a threat to any small fish in
the tank as well as almost all aquarium plants.
So while they're widely sold, they do need to be kept in a very
large tank, realistically 180 cm/6 feet from the left to right. In
anything smaller they're not going to do well and will likely cause
problems. At the very least, they'll simply look stupid wedged into
a tank where they can't actively swim about freely.>
What other fish would do best with them?
<In the right aquarium, Silver Dollars mix well with bigger but
peaceful companions, typically things like large South American catfish
and large barbs. While they may be viable alongside cichlids, this does
depend on the cichlid species in question, and some Silver Dollar
species can be nippy, so can cause problems with long-finned cichlids
if you don't select your Silver Dollar species carefully.>
I tried to find a list of compatible fish with silver dollars but I
don't trust what I find on Google (as advice from random people so
often conflicts with what you guys say) and I didn't find it on
your site (I apologize if it is up there and I overlooked it). Would
Tiger barbs work? How many?
<If you have 150 gallons to spare, then sure, half a dozen Silver
Dollars alongside 12-20 Tiger Barbs could work. Tiger Barbs can be
pronounced fin-nippers, but in large schools this doesn't usually
cause serious problems -- it's when people keep fewer than a dozen
specimens they find Tiger Barbs trouble.>
I stumbled upon the website aqadvisor.com, do you think I can go by
what their recommendations say?
<I have no idea. Don't have the sort of time required to test
out this website properly. Looks clever though!>
I basically want a large schooling fish (not Angelfish) that will do
well in a community tank. Am I correct in thinking that mollies and
silver dollars don't do well together?
<You are indeed correct. Mollies need hard, alkaline water, and
ideally slightly brackish water at that. Silver Dollars need soft to
moderately hard, slightly acidic to neutral water. There's no real
overlap between the requirements of the two species, and a tank that
was healthy for one would be stressful for the other.>
I really like mollies too.
<Mollies are best kept in an aquarium that caters to their needs. In
a 55 gallon tank that's easy enough to do, and you can then select
fish that will tolerate the slightly brackish conditions they
appreciate: Brown Hoplo catfish, Blue Acara, Horseface Loaches,
Australian Rainbowfish, Glassfish, Spiny Eels, etc.>
I do have experience with freshwater fish tanks but I am by no means an
expert. Any and all advice is greatly appreciated. Thank you
<Hope this helps. Cheers, Neale.>
Silver dollars fighting 10/7/2009
I have four silver dollars
<Groups of six or more, please.>
in a 72 gal. They have been together a little over two months.
(Other fish: 7 Serpae tetras (starters), 1 turquoise
rainbow-3.5", 1 male pearl gourami-4"-starting to
become more feisty, 1 platy-2"(starter), 1 bushy nose
pleco-4", 1 clown pleco-2.5", 3 bamboo shrimp).
<An interesting mix of fish. Serpae Tetras tend to be nippy,
so watch them carefully. The others should be fine, though it
goes without saying that as schooling fish, Rainbows are happier
in mixed sex groups of six or more.>
The tank has been running almost 5 months and the water quality
is good. I do a 10-15% water change weekly, run two 350
Marineland filters, keep the temp. at 79. Two of the silver
dollars have red anal fins (I guess they are called anal fins,
they are the fins underneath the fish towards the back),
and the other 2 don't really have any color on their anal
<Hmm... if these are Metynnis argenteus or some other Metynnis
spp., then it's the males that have red anal fins.>
One of the red anal fins is 4" in diameter and the other is
about 3.5". The other 2 have the same measurements. About a
month and a half ago, the two colorless ones developed 2 black
spots on their sides and the edges of their tail fins/top fins
also turned black.
<Do look at Metynnis maculatus, which has black spots on its
Metynnis argenteus sometimes has very small speckles on its
flanks, but not really big spots. Metynnis lippincottianus is
another option too; while similar to Metynnis argenteus, it tends
to have bigger spots on its flanks. Myleus rubripinnis is also
sold as the Silver Dollar sometimes, though its red, hook-shaped
anal fin should help tell it apart. Spend a little time on Google
comparing photos. While I'd be surprised if you had multiple
species in one batch of fish, it's not impossible.>
They have been acting more aggressive towards the other 2 silver
dollar, with the bigger one being the most aggressive. These two
have often been rubbing against one another. I'm confused, I
thought the ones with the red anal fins were the males, but they
get chased into corners and they stay out of it when the other 2
are rubbing and fighting.
<Well, yes, the ones with red fins usually are males if
we're talking about Metynnis argenteus.>
Are the 2 with the black spots both males fighting for dominance,
or male and female?
<Difficult to say. When kept in groups less than six,
"all bets are off" when it comes to behaviour:
schooling fish simply don't work as they should in too-small
groups. In a nutshell, schooling fish try to establish a pecking
order. In big groups, no one fish can bully all the others all
the time, so a sort of peace reigns. But if you have too few, you
make it easy for a bully to cause trouble, and their schooling
instinct doesn't work.
Try adding some more and see what happens.>
They are often going at it while the other 2 pick a corner until
it's calm again. I have also noticed that the 2 with black
spots will periodically go over to the other silver dollars and
nudge or nip at it, then go off again to rub and fight. This has
been going on for the past 2 months. I assume it is some kind of
breeding behavior, but shouldn't it be over with by now? I
have not seen any eggs, will they just keep going until some eggs
are deposited.? I wasn't to concerned before, however, now
I'm starting to see more ragged fins with no end in site.
Should I let the behavior run its course, or do I need to do
Thanks for any info
Re: silver dollars fighting 10/7/2009
Thanks for the quick response,
The tetras have been behaving and only fight amongst themselves
and the Gourami has taken over the tank.
The Gourami doesn't beat up any one fish but they all know
I attached a few photos, maybe they can help with
<Actually, they look rather odd, and not any species I'm
Myleus schomburgkii has a black vertical band on the flanks, but
a bit further back along the body. They certainly aren't the
Red-Hook Metynnis, Myloplus rubripinnis; the anal fin is all
wrong for them. The two common Silver Dollars, Metynnis
hypsauchen and Metynnis argenteus, have the right body shape and
the red anal fin, but not the spots on the shoulder like yours.
Metynnis maculatus has lots of spots, all over its body.>
The two that develop the spots (also red throats and black edges
on fins) don't always them. They seem to change almost
instantly when they are ready to do battle, which most of the
time during the day. I was afraid of adding more because I
didn't know if there was enough room left. I'm not
getting a bigger tank any time soon, however, if adding more with
bring peace, then I'll do it.
<I suspect adding a couple more will be helpful.>
| All plastic plants... I'd feed some greens.
Re: silver dollars fighting
I plan to pick up 2 more silvers dollars. If there is a
selection, should I get 2 like the aggressive ones with the spots
or 2 like the others? Does it matter?
<I'd get two of the *less aggressive* sort, on the
assumption this will minimise bullying by dividing up the
attentions of the aggressive fish among a larger number of
non-aggressive fish. Cheers, Neale.>
Re: silver dollars fighting 10/22/09
I recently added two more silver dollar. The store had one large
red hook and three small common ones. I bought two of the common
ones. They are only about a fifth the size of my current guys.
They haven't schooled with my big guys yet, but they are
starting to become more comfortable.
<Only members of the same species school, so it's
important to make sure you buy the same kind as whichever ones
you already have.>
The turquoise rainbowfish is bossing them around a bit. He
doesn't nip, he's just pushy. I guess he wants to show
them that he was there first and he's bigger and badder.
<Rainbowfish should be kept in schools as well, and kept
singly, yes, their behaviour can be aberrant.>
The first day they were in corners, now they just move when he
comes by then go back to doing what they doing. I was wondering
if I could add one more fish - an angelfish.
<I wouldn't mix Angels with Serpae Tetras; Serpae Tetras
are notorious fin-nippers, and I wouldn't ever keep them in a
community tank. These were my first ever tropical fish -- and I
learned about their shortcomings the hard way!>
Would the pearl Gourami not like that?
<Usually, Gouramis and Angels get along fine, given adequate
Would the angelfish become a problem as it grows?
<Pairs certainly become territorial, and single mature males
possibly so, though not usually.>
I'm looking to add one more nice looking fish, the angelfish
fits that description. If the angelfish wouldn't be a good
idea, do you know of one that would work?
here's my community again: 6 silver
dollars-4.5",4",email@example.com",firstname.lastname@example.org", 7 long-fin
Serpae tetras, 1 turquoise rainbow-3.5", 1 male pearl
gourami-4", 1 platy-2", 1 bushy nose pleco-4", 1
clown pleco-2.5", 3 bamboo
<Hope this helps, Neale.>
Re: silver dollars fighting 10/27/09
I had to remove my turquoise rainbow fish. I put him in my 10
quarantine tank. He immediately attacked the 2 new small silver
dollars, then preceded to harass 3 of the other 4 silver dollars.
I had noticed him hanging with my silver dollars lately. Maybe he
thinks he's a part of their group. Anyway, he would not let
the 2 new guys school with the other 4.
When I removed him, the 2 new guys looked so relieved they
explored every corner of the tank and began mingling with the big
guys and the big guys immediately started becoming more friendly
to one an other.
<Yikes! Sounds quite the disaster story.>
What do I do about the rainbowfish? I would really like to keep
it - it looks quite nice, but I don't want a rampaging fish.
I would consider selling it. Would it calm down after a few weeks
<Often this does indeed happen. As Bob says, "a spell in
solitary takes the fight out of them". Put in more
biological terms, he's removed from the social group and from
a familiar environment. When returned, he has to re-learn his
position in the pecking order, and usually the fish that are
already there will have the advantage. So yes, it's well
worth a shot.>
or go back on the attack? I'm at my stocking limit as far as
the inch per gallon rule goes, so I don't have room for 5
<Indeed, adding a few more, maybe even 3-4, would