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FAQs on Silver Dollars Systems

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

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>

Temperature Range - Metynnis and Rams? Sys., comp. - 09/30/2006 Hello y'all, <Hi.  My apologies for the delay in reply; I've been out, and your email came to us in a format that unfortunately our Webmail system had some trouble with, and I am one of the only folks able to respond to it.> First of all, thanks as usual for your maintenance of a wonderfully informative site. <Thank you very much for these kind words.> (I recently wrote my comprehensive exams for a PhD in education, and cited this site as a great example of a constructivist learning environment. So thanks for your contribution to my degree as well.) <This is high praise indeed - thank you again.> I would like to keep Metynnis hypsauchen and Microgeophagus ramirezi together in a 150 gallon system. <Maybe possible in this size system, given enough plants and hiding spaces....  but do keep in mind that the rapid schooling and darting about of the Metynnis may be stressful to the shy rams.  This is something I, personally, wouldn't try, but I imagine it can be done with success in as large a system as this.> My plan is to keep the temp at about 80-81° F, as this seems to be at the upper limit of the silver dollars and the lower limit of the rams. <The rams can go lower if you don't intend to breed.  Warmer would be preferable for them, but I'm rather concerned about the warm water making the Metynnis even MORE quick and spazzy.> However, I'm concerned that much of the literature about rams stresses that they're delicate, and happier at temps around 85. <Indeed.  But I would not bring the Metynnis to this temperature.> Should I: a) go with the "intersection" temp of 80-81 b) keep the temp higher, on the theory that the silver dollars are more tolerant of out-of-range temps than the rams c) not keep the two species together? <....  I would choose "C".  But again, that's just me.> Thanks again for your help and patience. <And you, again, for your kind words and consideration!> Melinda Johansson <All the best to you,  -Sabrina>

Arowana and Silver dollars in a big planted tank, sys.  2/29/08 Hi, I have a question that has many different angles to be looked at. I have been reading your website for the past 2 or 3 years and have scoured about 50% of the freshwater info as I have found it invaluable. First off, I have a pretty big L shaped aquarium, 8 ft long, 45 degree angle of 4 feet, then another 45 degree angle of 8 feet with the tank being 2 feet deep and 2.5 feet tall acrylic tank (about 900 gallons +/- 50 from evaporation etc.). Ammonia and nitrites are of course zero, nitrates are between 20 and 40ppm (attributed to nitrate factory type trickle Bioball sump), pH at a steady 6.8 attributed to the large pieces of driftwood I have in their and their tannin releasing ways, hardness is at 80ppm. Temperature ranges from 74 to 76F in the mid to upper levels, 72-75F in the lower levels, due to lighting I guess. Filtration turns the tank over about 5-6 times an hour, though with cloggy filters, maybe only 3 times an hour. <Does sound like you need to upgrade the filtration a bit; in all honesty jumbo fish need all the turnover you can get. I'd be looking at 6x turnover minimum, and likely 8-10. If water quality is basically sound, you can perhaps get away with just adding a powerhead or two into the tank to keep the circulation of the water even.> It currently houses a foot long silver Arowana and a school of 11 silver dollars (the smaller 5-6" ones, not the red hooks). I also have 4 fairly young (only 1 foot tall, about 20 leaves) Amazon swords planted in 2 inches of gravel, and a whole bunch of Anacharis that's growing like a weed (for the silver dollars munching pleasures) though it is growing much faster than the fish are eating them. <Sounds great!> I also have some powerful full spectrum lighting across the two 8 foot lengths of the tank, nothing in the middle of the L. My more concerning question, or more likely, situation, is that my Arowana (I've had it since it was around 5") recently started taking dives at my silver dollars as they swim on their merry way beneath him. Is this a show of territoriality or is he trying to eat the silver dollars or both? <Either. Both. Arowanas are territorial and object to anything in "their" zone of operations. This varies with species, and Silver Arowanas are very much at the mild end compared with, say, Scleropages jardinei. But on the other hand that doesn't make them friendly community fish! If the Arowana is sufficiently big, it may be trying to eat them, or at least "sample" them to see if they're edible. A 6" Silver Dollar is borderline when it comes to safety with an adult Arowana. Some people have mixed them fine, I know; but look at how big the mouth of an Arowana can get! I wouldn't be 100% comfortable with this combo.> The silver dollars are way faster than him though so I have not yet scene what happens when he catches them. He is usually just silently sitting beneath a carpet of Anacharis during the day and only moves when fed (Hikari Arowana pellets plus weekly beef heart, plus whatever flakes, crumbles, bloodworms I feed the silver dollars) or when the lights are off. Also, I read that Arowanas generally leisurely patrol the aquarium all day and I figured now that I finally built my uber aquarium (oh that's right, self made... 20% of the retailers price... plus several cases of beer and pizza for friends who assisted in heavy lifting. <Ha!> Is it possible that my lights are too bright and the Arowana doesn't feel safe or its hurting his eyes, though he did just swim around normally for about a month until he started to "hide"? They are power compact fluorescents, 525 watts per light fixture, 4 total fixtures. This is a major concern to me as I have been keeping fish for the better part of a decade wanting an Arowana but refusing to get one until I could house it properly and now he just sits there. At night I have moonlighting and he does then move around quite a bit, this is why I suspect the lighting, but I never thought they were nocturnal... more diurnal from what I read. <Difficult to say on this one. Arowanas are noted for being photophobic, though most fish prefer shade to bright light. Do all the lights come on at the same time? Sometimes fish get alarmed by that, and having the lights come on across an hour makes a big difference. It does sound like he doesn't like the light. Is adding an understory of plastic plants (there are some great 3' plastic plants available now) an option? Something that could drape across the surface and cast some more shade? I suppose the experiment would be to unplug one light fixture for a day or two, and see if the Arowana prefers that end of the tank.> My next question has to do with the silver dollars and them seeming to enjoy eating the Amazon swords more so than the Anacharis. Is there some other large show plant that does well under high lighting that the silver dollars wont want to eat? <I'd perhaps look at Crinum spp., e.g., C. calamistratum, as these do seem to be left alone by herbivores. They're big and generally hardy. Java fern will do great under bright light, though it does tend to become an algae magnet. Anubias even more so.> Also, my swords aren't exactly growing as well as they had in past tanks with 4-5 inches of gravel. Does the gravel depth make that much of a difference? <Yes; also the quality/composition of the substrate.> I have something like a thousand Malaysian trumpet snails aerating the gravel and what not but am concerned that if I add more, the snails just wont be able to irrigate and aerate all that gravel, and the last thing I want is some anaerobic environment unreachable by plant roots or snail burrowing releasing poisonous hydrogen sulfide and the likes into my tank, plus stinking up my fish room. <Just doesn't happen. The "anaerobic decay" thing is largely a myth. Happens naturally in ponds and in marine tanks (inside living rock) and no-one fusses. So by all means ramp up the depth of substrate to what worked before. Do also check first that the substrate is adequate though -- Amazon swords want a nice rich soil or Laterite enriched substrate, and plain washed gravel just won't work for them.> Should I consider ditching the silver dollars for a school of tinfoil barbs? They don't eat plants at all do they? <Tinfoil Barbs can, will eat plants.> And lastly, as you may have guessed it, I want to add more fish to this tank as it seems fairly empty... I'm thinking black ghost knife? <In theory fine, but you'll be hard pressed finding an adult large enough for this community. Mostly you only see baby Apteronotus for sale.> I first filled up the tank about 8 months ago, filling it with something like 100 Malaysian trumpet snails and about 20 mystery snails for my tank cycling. I over fed the snails for 3 months in order to obtain the current population explosion of snails I now have, <Consider adding a group of Clown Loaches or thorny catfishes (Doradidae). These will eat the snails, if sufficiently hungry.> at the end of month one I added the sword plants, then I added the silver dollars at the end of month 3, all at about the size of, well, silver dollars. They mostly hid in the center decor castles of my tank for the first two weeks but then began to sprint (if you will) from one end of the tank to the center and back (they seemed to never travel into the leftward portion). After having them in there for 2 months, they had grown to about 3" in diameter each and I added my Arowana at 5". After only another 3 months the Arowana (from what I could tell) doubled in size, which I attributed to it having so much space to swim. <Or simply good maintenance. Arowanas grow quickly if kept well.> Now I added the Anacharis about 2 weeks after the Arowana was added and it was generally ignored by all but a couple of snails. Then a month ago (beginning of month 7) is when the Arowana began to just sit under the Anacharis. So yeah, back to the black ghost knife... I want to buy two of these guys (I figure the tanks big enough) and I put two PVC condos with 15 pipes of 2" diameter and 1' length in there, one in each 8' portion. Should I be concerned about the Arowana eating them as I often find the knife fish around 4-5 inches in length max, and it will be some time before they grow to their 2' potential where the Arowana wont (hopefully) eat them. Are the black ghosts fast enough to evade the Arowana if pursued? <No; sooner or later, if they're small enough to swallow, they'll be eaten. The Arowana only has to get lucky once!> And for the record, despite clown knives growing huge and not being swallowable by my Arowana, they will probably eat my silver dollars and knock over my plants, and just grow too big for my taste, so that options out. <I agree.> Well, that's all for now. I literally read all over the web for months and abstained from just writing you guys since I know how annoying it can be to be asked simple questions that have their answers everywhere... but I just cannot find anything like this Arowana diving at silver dollars thing while not swimming anywhere else. I am a student of the sciences, my job being that of a biochemist, therefore I was cocky, stubborn, and reluctant to ask for help (a character flaw repeatedly pointed out by many over the years)... but there are just some things you cannot learn in books. I'll likely have another question or comment in a couple of months after the knife fish are added... if they are compatible. Thanks in advance for any advice you can provide. With Best Regards, Matt <Hope this helps, Neale.>

Re: Arowana and Silver dollars in a big planted tank (RMF, please comment)  2/29/08 Well It looks like I'm going to be upgrading my sump pumps using some pond pumps to get that water flowing up to the 10 times over level. I currently have four overflow filters going into four 55 gallon tanks... I guess I will just have 4 extra pumps to sell on aquabid.com as I replace them with the pond pumps. The pumps I have looked at are reporting 1800 gallons an hour (Danner Supreme Mag Drive Aquatic pumps, I currently own the 1200 gph pumps)... am I going to need larger sumps or will this push through the 55 gallon tanks just fine? <No idea; RMF, any thoughts?><<I would definitely be reading, making careful choices here... There is much to be saved in the way of electrical cost, pump noise, waste heat, service life, by making good decisions re pumps... The Sequence series/Baldor motored lines are some faves for the size, application here. Other fractional horsepower pumps are ably reviewed here on WWM: http://wetwebmedia.com/pumpselmar.htm and the linked files above. RMF>> This company also sells a 5000, specifically designed for large ponds and waterfall displays which reports 5000 an hour. Is that overkill or should I add one or two of those in too? I guess two 1800 and two 5000 gives me 13600 gallons an hour claiming about 15 times an hour for the whole tank... realistically maybe 11-12 times an hour turnover? <Probably overkill. 8-10 times turnover should be adequate.> As for the silver dollars not being fully compatible, I will look into giving them a new home. I have just been keeping silver dollars for 7 years now and figured I was pretty good at it. My last batch of 7 didn't die, with the oldest being 5 years old starting in a 55 gallon and moving up to a 120 gallon for the remainder. I just gave them to the LFS before I moved halfway across the country for the job that would allow me to have such a lavish aquarium. What other fish come to mind, that would be an attractive school of 15-20, that could be raised in one 8 foot section (separated by a divider) until large enough to not be eaten by the Arowana? I'm thinking Bala sharks? <A good choice. But also Semaprochilodus taeniourus look amazing in large groups, and are nice Amazonian fish.> I read they get to 12-15" and from my limited experience, are very fast. <Oh yes.> Do they eat plants because I cannot find info saying that they do, but then again, I was wrong about the tinfoil barbs. <Balantiocheilos melanopterus generally ignores plants. It eats green algae and invertebrates, and may nibble on tender shoots, but that's about it.> Maybe 6 months separated, grown to 7-8 inches then set to survive with the Arowana? <You may also be able to get adults via Fish Forums, fish clubs, etc. Lots of people buy them, and then have to rehome them when they get too big.> Are their any other fish you could recommend as I have limited experience with large schooling fish. <There are a lot of nice big barbs. Severums would also look quite nice, and occupy the midwater. They're territorial when spawning, but your tank is big enough that shouldn't be a problem. What about catfish? Sorubim lima is a nice big (45 cm/18") schooling catfish. It's very peaceful, pretty, and quite easy to obtain. It famously likes to swim vertically leaning against plants and rocks, so is definitely fun.> As for the lighting, the timer IS set to go on all at once come 10am and turn off at 8pm. Some sunlight does come through the one window and glass door to wake the fish up, but I guess that is nothing compared to a full 2000+ watts blazing into their eyes all at once. I can turn on the actinics at 10 am, then 2 of the other full spectrums on at 11, and the rest at 12... and then shut them off in the same manner (off to Home depot again for more electric timers). I assume this will still be ample light for the Anacharis and Amazon swords. <Should be. Try it, and see what happens!> And I do have two 3 foot plastic plants draping across the top of my tank which cover an area of maybe 4-5 square feet each. They are located in between the Amazon swords as to not rob them of light. I don't really want to put much more over the plants, but there are still many other places in the tank to add another 4 to 5 of those 3 footers without disrupting light to the live plants. I will give them a try since they are cheap and fairly realistic looking. As for the other plants, I do have an Anubias growing on a piece of driftwood, though the plant is 3 years old, started as 3 leaves, has maybe 30 now, and has only moved about 1 foot across the driftwood (3 foot long driftwood). It used to be house with a Pleco so perhaps his constant sucking of the driftwood would constantly cull the Anubias... or maybe the thick film of algae growing on its leaves is inhibiting it? <I've tried Anubias with my Panaque, and it gets turned into a Swiss Cheese Plant, so I agree with you here!> Ill try out the C. calamistratum when I find it. If nothing else the LFS can order it for me. <Mail order plant distributors abound, and this is a fairly common species, at least here in the UK.> I do have a Sailfin Pleco in there too. He's only about 8 inches long though so he is having a problems stopping all the algae as of yet, though I have faith in him (or her, I cant tell yet). <Once they mature they aren't really algae eaters, so don't hold too much store by this. Plecs generally are omnivores, and algae is only a part of their diet.> As for my substrate, it is just painted black artificial gravel. I add trace minerals for the plants, but I guess that's just not gonna cut it. <Indeed.> It will take some time to clean all 200+ lbs of gravel out, but I would say in half a years time I should have 4 inches of Laterite enriched substrate in there. <Can't begin to tell you how much I sympathise! Anyone who has grown aquarium plants (or tried, at least) will have been through the mill of changing substrates.> I guess I wont be getting the black ghost knife anytime soon, if ever, aw well. <Again, look out for "second hand" specimens.> Maybe I'll get some water in my 120 and raise him in there until he's big enough for the show tank. <Quite.> And perhaps I misspoke about the snails as a pest, as I want them in their. I have never been able to keep a tank as clean as I do when I have snails in their. <I wonder if Apple Snails would help on the algae front?> I once had a tank with 4 yoyo Loaches in there that cleaned out the snail population, there was a gradual decline in water quality, and an increase in detritus and algae that I fought for a year... I removed the loaches to the LFS and my tank recovered to crystal clarity in 3 months time. <Not impossible.> Therefore, largely based on this single experience ( I know, that's poor scientific form) I like to always have snails. And despite the appearance of (now about 100 mystery snails) snails crawling all over my tank with about 1 snail on every 4 square feet of glass (or I guess acrylic), I find it more peaceful and artful than an eyesore. <Indeed.> It looks to me as though your experience in the trade has done it again. Thank you very much for your assistance. Matt <Good luck, Neale.>

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