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FAQs on Jack Dempseys Systems

Related Articles: Jack Dempseys, Oscars, Neotropical Cichlids, African Cichlids, Dwarf South American Cichlids, Cichlid Fishes in General

Related FAQs: Jack Dempseys 1, Jack Dempseys 2, & FAQs on: Jack Dempseys Identification, Jack Dempseys Behavior, Jack Dempseys Compatibility, Jack Dempseys Selection, Jack Dempseys Feeding, Jack Dempseys Disease, Jack Dempseys Reproduction, & Oscars 2, Neotropical Cichlids 1, Cichlids of the World, Cichlid Systems, Cichlid Identification, Cichlid Behavior, Cichlid Compatibility, Cichlid Selection, Cichlid Feeding, Cichlid DiseaseCichlid Reproduction,


new setup for Dempseys
Electric Jack Dempsey Set Up    5/16/14
I will be honest I feel silly I can not find the answer to this question.
I have two electric blue Jack Dempseys. They are being upgraded to a 65 gallon aquarium. Currently they have inhabited a 20 gallon long tank with 0 ammonia and nitrites and ranging around 20ppm
< Nitrites are very high at 20 ppm. If you meant nitrates then not too bad.>
Anyway the question is about the new tank I bought for them. I am trying to research the best setup for them hence the first question. I know they aren't African cichlids but what region are they from? Are they South American?
< The true wild fish come from Central America.>
The reason I am so curious is that I want them to have the best and for substrate I wanted to go with something live. I have been told the African cichlid types of sand would be to aggressive in terms of hardness and alkalinity. One lfs advised me to use eco complete substrate even though I am not doing live plants. One mitigating factor is they reside with an African clawed frog, thus far they have totally ignored one another getting along quite famously. I do hand feed them all so I am not to concerned about the frog ingesting the substrate but he isn't the brightest bulb I would not put past him eating anything, the fish are significantly to large to ingest. So what type of cichlid are jack Dempseys?
< They are a line bred cichlid from the tanks of aquarists in Argentina.>
So that I might accurately research them. Also what substrate would you recommend? I prefer live because of the success I had with saltwater live sands and I am interested in cutting cycling time to a minimum. Thank you in advance.
< Go with any substrate you want. I would recommend a coarse sand or fine gravel. Use the old filter on the new tank at the same time you use the new filter on the 65 gallon. The old filter will have the bacteria needed to get the new filter going so you will have some biological filtration. Take the old filter off in a couple of weeks. The live sand really isn't needed.-Chuck>

Salty Electric Blue Jack Dempsey    10/26/11
<Hi there Kyle>
I have a juvenile Electric Blue Jack Dempsey as the only inhabitant of a tank heavily planted (for now) with wisteria. I know that many freshwater fish and plants can adapt to mildly brackish conditions,
but I was curious about how salty the water could be before negative side effects and stress took their toll. I have no plans to do anything foolish, as I raised the Jack to his current 3.5" size from a baby (.5"), and needless to say I am attached, but I would just like to know if it was possible for the fish and
possibly the plants to adapt to brackish at all.
<Only to slightly brackish... a few thousandths... Bob Fenner>
Thank you for your time,
Re: Salty Electric Blue Jack Dempsey  10/26/11

Thanks Bob!
<Welcome Kyle>
So if I gradually upped the SG to 1.003, would a violet/dragon goby be able to cohabitate if the Jack was willing?
<Would be close. BobF>
Re: Salty Electric Blue Jack Dempsey  10/26/11

It would definitely be an odd pair. May experiment at some point haha.
you again for your time.
<Welcome. BobF>

70 Gallon Tank  8/4/10
Hi there, I have a 70 gallon tank, empty right now and has been cycling for a few months with regular water changes. I am very interested in the Jack Dempsey cichlid and was wondering if one would do well in my tank.
Also, I have read a bit about them, but am unsure of whether or not I can keep more than one.
<One or a mated pair.>
I have read online that they can grow to about 10", but most only grow to about 7" or 8".
<This is true. The JDs in the trade are very stunted compared to the wild fish, and frankly their colours are usually pretty poor too. The problems are inbreeding and the fact people cross-breed any two fish rather than the two best fish, which is what would happen in the wild -- survival of the fittest meaning that small or dull JDs wouldn't survive or wouldn't attract partners. The "Electric Blue" JD is one way people have worked around this, though the resulting fish isn't to everyone's tastes -- it looks pretty garish really! If you want to keep JDs, here's my advice: Since these fish are so territorial, and keeping them with anything else isn't easy, you may as well get the best pair you can afford. Don't buy the fish ones you see, as these are often siblings from some local breeder. They'll be small and dull. Hunt for good quality specimens. If you can, inquire through your local fish club, or search online, for either wild-caught or F1 specimens.
What ever you do, take your time choosing just the right fish. Good specimens will reach a large size and will have lots more blue spots on their flanks that the el-cheapo ones sold in most pet stores. If you're going to have one species of fish in a big tank, and you're going to keep that fish for something like 8-10 years, you may as well stock it with the best possible specimens!>
Will mine grow to 10" or more if I give him my 70 gallon all to himself?
<Individuals do need quite a large tank, yes. Once settled down you may find your specimens are tolerant of Suckermouth catfish and perhaps even fast-moving hard water dither fish at the top of the tank, such as swordtails and Mexican tetras. But others are extremely aggressive, and all JDs are somewhat piscivorous. Rearing juveniles together can help them to tolerate tankmates, but there are no guarantees.>
I have read many stories online of people successfully keeping two Dempseys in the same tank, but I don't want to risk my fish being unhappy.
<Pairs work extremely well, and these are classic laboratory cichlids used for behavioural experiments; for example, you can read up on them in 'King Solomon's Ring' by Konrad Lorenz.>
What do you think? Should I just stick to one? Also, will my tank be large enough, too large? I love the fish, the colour and the personality! I have previously kept Oscars and enjoyed them thoroughly, then kept discus. I am
getting out of discus keeping and now face a toss up between getting a Dempsey (or two) or another Oscar. Any advice would be greatly appreciated!
<Good luck! Neale.> 
Re: 70 Gallon Tank  8/4/10

Thank you so much Neale! You have great advice!
<Happy to help.>
Regarding selecting my Jack Dempsey, how can I tell their genders?
<Notoriously difficult. The only reliable way is inspection of the genital papillae, which are narrow and pointed on males, short and blunt on females. Some people will maintain that males have more blue colour and longer or more pointed anal/dorsal fins, and that may be true much of the time -- but there are plenty of exceptions! Juveniles are virtually impossible to sex.>
I am going to look at some this weekend, a breeder is getting out of cichlids and giving away all of her fry. How can I tell which fry are male and which are female?
<You really can't.>
I would love to have a pair, but don't like buying a lot of fry just to keep two; but if I have to I will.
<As with sexually monomorphic cichlids generally, the "buy six, keep two" approach is the most reliable. But yes, it's also a hassle.>
I am still debating whether or not I want Jack Dempseys or Oscars.
<Oh, the Oscar is a far better "pet". There are a dozen cichlids I'd choose before JDs without even a moment's pause. Look at the Rotkeil Severum for example, or the Chocolate Cichlid Hypselecara temporalis. If you can find them, Canara Pearlspots are stunning fish, and good quality Aulonocara are always a pleasure to keep.>
My husband seems to be leaning towards an Oscar, so I guess we'll see. I will go look at the Jack Dempsey fry and see how they look.
<Good plan.>
What do you think about keeping an Oscar in my tank? It would be large enough for one, correct?
<55 gallons for a juvenile, 75 for an adult, especially if you want to add a catfish.>
I enjoy how much personality they have, despite how messy they are!
<Nothing a decent reverse-flow undergravel filter won't fix.>
Thanks again Neale! Lena
<Have fun! Cheers, Neale.> 

Changing fish in tank from koi to Jack Dempsey 8/9/09
We are very impressed with this forum and would like to ask for some advice.
<Thanks for the kind words.>
We have a well established 55 gallon tank with 2 butterfly koi, 2 large 6" plus goldfish and 1 Plec. We are relocating these fish to the pond would like to change the tank to one Jack Dempsey and the Plec.
<Should work, provide the Plec has a decent "cave", and the JD doesn't feel threatened. If you can, use a bunch of rocks to create a variety of hiding places. Granite and slate are safe and inexpensive, and you can buy these from garden centres for a fraction what they cost in pet stores. Just be sure to choose "pond safe" rocks (any decent garden centre will know what this means) and check any rocks lack metallic seams, as these can pollute the water quite seriously.>
We use a Rena xp3 canister filter and monitor the water conditions.
<The Rena XP3 has a turnover of 350 gallons per hour. That's a bit over 6 times the volume of the tank per hour. That's a good starting point, but if you find there's a lot of gunk floating about, you might care to add a
second filter. Optimal filtration for a 55 gallon tank containing two big, messy fish would be 8 times the volume of the tank, which for a 55 gallon tank = 440 gallons per hour. So a second filter rated at 100 gallons per hour would be a sound investment.>
We were advised by our local aquarium store that we should not have any problems and would not need to completely restart the tank. We have another 70 gallon tank with a variety of South African cichlids, but have never owned a Jackie Dempsey. Do you have any advise?
<JDs are "old favourites" -- they're hardy, adaptable, colourful, and generally not shy. But they are very aggressive, and being territorial, can be bad tempered. They work fine with Plecs, given space, but just bear
their "crankiness" in mind. Do also shop carefully. A cheap JD may lack the colours that make big cichlids worth keeping, so shop around, and perhaps ask around at a regional or national cichlid club for the names of good breeders. If you're going to set aside a big tank to what is essentially just a one fish aquarium (the Plec will be hiding all day) you may as well get the best JD possible. A wild fish would be ideal!>
We have another 70 gallon tank with a variety of South African cichlids, but have never owned a Jackie Dempsey.
<They are nice fish, and as far back as the 40s and 50s considered essential fish for the armchair naturalist. They feature in, for example, "King Solomon's Ring" by Konrad Lorenz, probably the most important and
influential book on animal behaviour ever written for the non-scientist.
Mated pairs are superb parents, as good as any to be found in the animal kingdom. On the other hand, they are famously bad tempered, though perhaps not as aggressively destructive as some of the other Central Americans such as Red Devils. As with all Central Americans, they need hard, basic water that isn't too warm. Do see here:
Thank you....Donna
<Cheers, Neale.>

Re: Changing fish in tank from koi to Jack Dempsey 8/9/09
Thanks so much for the advice. We'll invest in an add'l filter system and rock/cave material, and research JD purchase as you advised. ...Donna
<Very good... keep reading, and when you're confident you've found a handsome JD (or perhaps a pair!) snap them up. Enjoy! Cheers, Neale.>

Jack Dempsey Tank I'm setting up a tank full of Jack Dempseys I have six and its a 55 gallon tank so I was wondering if you guys can help me with the set up of the tank because I would like to make the tank look great and be healthy for the fish. I would also like to know what other types of fish I could put in. Right now I only have one Pleco. I need to know if I should have caves so they can have territories or what else I should do. I've been looking for info but haven't found anything I need your help. < No problem. That is what we are here for. If you have the real Jack Dempseys then they can be sexed at about two inches. Females are smaller than the males. Females have lots of blue on the lower jaw and less blue spangling on the body than the males. Males have longer fins too. After a pair are established then they will want to spawn. They are substrate spawners and will lay there eggs on just about anything.  When the eggs are laid they will guard the eggs and fry from all other fish. So they will corner the other four fish away from the spawn. Adults will excavate pits in the gravel as they move the fry around the tank. The other fish should be removed or they will be killed. No plants or at least artificial ones. Lots of rocks. A good outside power filter. A good heater that can keep the water at 78 to 80 degrees year round. Lots of quality pellet food. O know you didn't ask about spawning these fish but with 6 fish your chances of getting a spawning pair are about 98.6%, so get ready.-Chuck>

Jack Dempsey Cichlid Set Up 7/27/05 Hi I'm looking to buy 3 2 inch jack Dempseys for my 55 Gallon tank. Which would be best to get in the way of breeding, 2 males and a female or 2 females and a male. And would 55 Gallons be enough room for all 3 fully grown? Thanks < Get two females and one male. Females have lots of blue in their lower jaw area where males have hardly any. Males also tend to get bigger, have more color on the body and get longer fins. They may spawn between 3 and 4 inches. The male may decide to spawn with both females in each end of the aquarium. If they continue to spawn on a regular basis they will grow slowly because they are putting all of their effort and energy into spawning and not growing. After a couple of spawns the male may turn on the female and kill her if she is not ready to spawn. In this instance you need to separate the two and try to breed them using a divider method. Adult jacks Dempseys will get up to 10" for the males and around 6 to 7" for the females. This means you would need a 75 gallon tank if they were getting along and a 125 if they weren't. Don't worry though. You will have spawned then many many times by then and probably looking for other fish to work with.-Chuck> Moving A Jack Dempsey - 10/19/2006 <<Hello, Dennis. Tom with you today.>> I have a Dempsey that is about 7 inches or so, he is in a 35 gal. tank currently. I was finally able to get my hands on a 72 gal. tank for him. <<You'll both appreciate that!>> I currently do not have a water heater and never have had one, is this something I should consider getting for him? If so what temperature is the Dempsey comfortable in? <<Depends on the climate you live in, Dennis. Dempsey's are tolerant of cooler temperatures than we might normally associate with these fish but the mid-70's F. should do quite well. The big factor, as you may be aware, is keeping the temperature stable, i.e. no 'bouncing' around even within the range the fish does well in.>> Second, I would like to get another fish if not 2 more, some sort of cichlids preferably, but I am not sure what would be compatible with him. Do you have any suggestions as he is a pretty aggressive fish? I had an algae eater they he has already killed after about a week. <<The trick, if you want to call it that, would be getting your hands on an aggressive species that will stand up to a nearly full-grown Dempsey. Convicts and Green Terrors are examples that come to mind but, again, might not fare well as juveniles. His aggression may dissipate in the larger tank, which I would expect, but I can't discount that you may have a pet that isn't tolerant of any company. The Plecostomus -- providing that's the type of 'algae eater' you had -- should have been okay with a Jack Dempsey, for what it's worth.>> Any help you can give me would be great. Thanks Dennis Smith <<I think the key here, Dennis, is to set your new tank up so that your Dempsey can 'stake out' a territory of his own. If your setup is too 'generic', he may simply lay claim to the entire aquarium and make adding a tank mate or two virtually impossible. Congratulations on the new tank, though, and best of luck to you. Tom>>

Moving A Jack Dempsey - II - New Used Tank - 10/19/2006 <<Hello again, Dennis. Tom>> Should I have any concerns setting up a 72 gallon tank for my Jack Dempsey if the tank was previously used as a salt water tank? Are there certain precautions I should take beforehand besides rinsing it thoroughly? <<Shouldn't prove a problem, Dennis. No soap, obviously, though I might try using a mild bleach solution to clean the tank. You'll want to do a "test run" on the tank, i.e. fill with water and check for any leaks, before setting it up to cycle and make sure that it's ultimate location will provide a level platform. Common sense stuff, really. Other than that, I'd say you'll be in good shape.>> Thanks <<No problem, Dennis. Tom>>

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