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I had two pearl gouramis in a 20 with a black ghost knife, and a couple of sword tails.
they did great for a while, acted completely normal, not skittish at all, and their colors were bright, and this last monday, they jumped hard enough into the lid of the tank that they broke their spines ( I could tell by the way their bodies hung.)

I can't think of a reason for them to have gone nuts like that, I've been keeping fish for most of my life, and have never had anything like this happen before. I checked the water and everything is normal, and the bodies showed no overt signs of disease.

any Ideas?

proud father of a bunch of baby haps. http://picasaweb.google.com/Sktchy/BABIES

Let me see ...

Two Pearl Gouramies, a Black Ghost Knife Fish and two Swordtails in a 20 gallon ...

You may think this is facetious, but they were probably trying to escape. Because they were painfully overcrowded.

Have you any idea how big a Black Ghost Knife Fish grows to be?

This is a 20 inch fish when fully grown. Once it piles on some body mass, it won't FIT in a 20 gallon. A long term home for that fish is nearer two hundred gallons.

Plus, the Black Ghost Knife Fish has another complication to factor into all of this. It's a fish that navigates by generating electric fields that spread out from the body. Which means that you have to be careful about placing certain electrical items too near the aquarium. One sure fire way of stressing a Black Ghost Knife Fish is to place hi-fi loudpseakers or a PC too close to its aquarium - the fields those items generate interfere with the fish's electric field and, basically, subject the fish to an ordeal that would probably constitute torture if you did the same to a human being.

The Pearl Gouramies are 5 inch fishes when fully grown. Ideally they need a 55 gallon setup to spread their fins, but in a 55, they'll coexist with the Swordtails (which also need a bit more space than a 20 to spread their fins if they're going to be truly happy, because I've seen some BIG Swordtails like you would not believe).

I do wish dealers would be more responsible when selling these fishes and tell prospective owners what to expect when taking them on. You didn't get your fishes from a large chain beginning with "W" by any chance?

For future reference, when choosing aquarium occupants, follow these guidelines:

Item number one : Do your research. Check the size that a fish will reach, and if it will outgrow your proposed aquarium, do not buy it. Likewise, check such factors as water chemistry likes/dislikes for your fishes, and behavioural compatibility with other fishes. In other words, don't buy an Oscar and stick it in a 20 with some Neons unless you WANT the aquarium to be a disaster area.

Item number two : Cultivate a dealer who KNOWS what he's talking about and is looking at making a successful fishkeeper out of you. Someone who will warn you against making a stupid purchase, and who will, ultimately, earn his keep by making you a fishkeeper who keeps coming back for more because his good advice helped you become someone who keeps fishes alive for decades. You stand as much chance of getting that kind of guidance from a supermarket as I do of being caught by the paparazzi in flagrante delicto with Scarlett Johanssen.

Item number three : Cultivate the good souls on this board. Some of us have been keeping fish for frighteningly long periods of time. I'm racking up, let's see, 32 years of fishkeeping now. Some on here are looking at over 50 years' worth of experience. Even some of the young 'uns on this board have impressive achievements under their belts (waves walking stick). So, some of the regulars on this board can offer you something like 2,000 years of combined fishkeeping experience. You'll be hard put to find that elsewhere in a hurry.


Panda Catfish fan and keeper/breeder since Christmas 2002

trust me sktchy,listen to cali,them black ghost knifes.get to big robust fish,ive seen them at like 35cm,and they looked big,and theyll get bigger than that

thanks for the well-informed responses! I appreciate it!

I'm well aware of how large the fish get, I'm also working on getting a larger tank set up so that once the ghost knife (currently only 3" ) is big enough to need it I can move him up along with the rest of that community.
it's a simple matter of them currently being in a small tank because they are small fish and moving up when they get bigger.
I have also had a ghost knife before, and kept him alive for a long time (10+ years in a 55, currently being used by my african cichlids.), they are slow growing, so I knew he wouldn't be too big for his tank for a while.
I'm not new to the hobby, I've kept fish for nigh on 16 years myself, and I have kept many a fish alive for at least 5 years. that said, thanks for your advice. your absolutely right that they would have needed a larger tank. like the 75 I'll have ready for them when the knife get's to about 5"
by the time he outgrows the 75 I'll have a bigger tank for him. closer to the 200 you suggested actually. (I don't recall ever seeing a knife that was 20" long, but if this one lives to reach that size, I can't wait! how gourgeous a fish that would be!)

and as for where I get my fish, it's at a local store where the owner has been keeping for nearly 40 years and is more than willing to offer plenty of advice. again, I'm not stupid, and I know better than to buy a fish from "W".

even if dad got his oscar there and put it in a thirty gallon community. much to the detriment of every other fish in the tank...(dad is e to less than intelligent fish purchases...)

anyway, I hope that didn't come out too snappy, it's just that you seemed to think I was new to the hobby or some such thing and I'm really not. looking at your posts on some of the other threads, I have to say I do respect your knowledge of fish, I'm impressed honestly. but I do know better than to overcrowd a tank that badly.

proud father of a bunch of baby haps. http://picasaweb.google.com/Sktchy/BABIES

People have no way of knowing what your experience is. Posting on a forum, with a lot of very caring and serious fish hobbiest, that you have a BGK and those other fish in a 20 gallon is not going to get you a pat on the back.

I acknowledge your point and admit that I should have been more thorough in my original post.
also I'm currently thinking I might be wanting to get that 75 going a little sooner than I had thought.

as I said, I probably got a little over-defensive in my last post, sorry about that.

*new question*
it occurred to me that if the ghost knife I had previously lived so long in a 55, that might explain why I've never seen one as big as you guys are saying they get, since a fish kept in too small a tank will experience a stunted growth rate and decreased health. so from your experience, how fast do they grow when given optimal conditions?

I really like BGK and I'm a little heartbroken to hear that my last one was probably under poor conditions in the 55 that it was in...

proud father of a bunch of baby haps. http://picasaweb.google.com/Sktchy/BABIES

Even when a fish is small it's good to give it a fair sized tank to avoid stunting it early. He'll never reach the 18-20" a ghost knife can if you stunt him while he's little. Lots of water changes also helps avoid stunting especially the smaller or more heavily stocked the tank they are in. You can't test for everything in the water but you can dilute everything with water changes. A nitrate test only gives you an idea of the condition of the water and if I had fish that were going to increase that much in size I'd probably be keeping nitrates below 5ppm with at least weekly and up to 3times weekly water changes until they were moved to a larger tank.

A pair of pearl gouramis could probably live in a 20g if there were no other fish but would be much happier and healthier in a 29-30g. An oscar will not fit in a 30g longterm. Not even very well for short term. They have alot of body mass and are quite messy. Eventually the oscar will need at least a 55g preferably a 75g pretty much to itself. It will eat most anything small enough to fit in with it so if it's a possibility one will be in your care I'd suggest looking at another large tank or convincing your dad to look at slightly smaller cichlids. Otherwise all the fish will be at risk of poor health and shortened lifespans. There are tons of other cichlid species out there. I had to research and print out information all the time to prove to my mom what she could and could not put in the 29g community I had in the living room.

the BGK is sadly no longer an issue...
anchor worm that I hadn't noticed...
he was laying dead in the tank when I got home from classes tonight...
I had him for nearly two months...
I feel awful right now...
anyway, just thought I'd let you all know...

as for dad's oscar, it is in a much larger tank now. and quite happy, at the cost of several tetras from the previous community...
the thirty eventually broke, and the oscar is upwards of 5 years old by now.

proud father of a bunch of baby haps. http://picasaweb.google.com/Sktchy/BABIES

well everyone we know now that he has kept fish b4,so next time we wont be so hard on you lol.also sorry to hear about your BGK.

ps,just 1 other thing,you said you are sad for keeping your old BGK only in a 55gal,next time even if you get 1 thats only like 2 inches long,throo him into like a 150 gal,then you will see what we were talking about.in a tank like that,with the rite tanksmates and food,i rekon 50cm no probs.

thanks Hokese I appreciate it, I didn't mean to be all snappy like that...
bad day, oh well...
hopefully no one will hate me too much for it...
next time I try a BGK I'll do better for it, I didn't realize they got quite THAT big, like I said, I've had them before but that one only got about 14", still a little big for a 55, but not so bad that I was worried about it...

proud father of a bunch of baby haps. http://picasaweb.google.com/Sktchy/BABIES

Black Ghot Knife Fishes are fairly slow growing even if they're given space, but if they're given space to start with, they continue growing in a better fashion than they do if they're moved on a frequent basis to 'incremental' aquaria. Remember they're pretty reclusive (plus they're nocturnal in the wild and need feeding after "lights out" when acclimatising them) so they tend not to like radical change to their surroundings. So if you give a baby specimen a 55 gallon aquarium from the start, furnished sensitively, then migrate it to a 125, say, once it reaches around 8 to 10 inches, then migrate it to a 200 or larger when it reaches around 15 inches (this latter stage will take some time even in a 125) then chances are you could end up eventually with an 18 or even 20 inch specimen. However, given the growth rate even in optimal conditions, you could be looking at the best part of 20 years before a baby Black Ghost Knife Fish reaches that size. Which means you are looking at taking on a fish that has the potential, if cared for properly, to be a part of your life for a quarter of a century. Put it this way, if I took one on now, I could find myself still saying hello to it first thing in the morning when I'm 70 years old. That's quite a daunting prospect for some ...

What makes this even more daunting in my case is that thus fat, I've had a habit of keeping fishes that live long lives. I've had Lemon Tetras live to be nearly 8 years old. Cardinals that live to be 7 and possibly a bit more. One of my Otocinclus catfishes was over nine years old when it finally went to the great aquarium in the sky. Given that the eldest of my Panda Corys is only 3 years old, the species is known to live to 15 in other people's aquaria, and in mine could live to be 20 years old if they follow the pattern of my other fishes (namely living to be older than usual because of the care I lavish upon them) then a BGK could, in my hands, end up living longer than me.

If you start a BGK off in a 55 gallon setup, then you have a good four years or more to plan the next stage (namely the 125), and possibly as long as 6 years. Once the fish has been migrated to the 125, you have another 6 to 8 years to plan the 200 or larger. In a 200 or larger, it's more or less settled.

By the way, here in the UK, keeping oddballs is a pastime that has some fans. Two of the best known in the game being Richard Hardwick (one of the people who writes for Practical Fishkeeping magazine here in the UK) and Sean Evans (take a look at his website here), whose collection includes a two foot Leiarus pictus catfish that takes food from his hand, a 24 inch Clown Knife Fish and a Hoplias malabaricus Wolf Fish that has jaws like a car crusher and looks like T.rex with fins! So you're in good company if you want to keep oddities like the BGK.

Oh, Richard Hardfick has Electric Eels in his private collection (300 gallon tank housing a pair of them!) and he recently took delivery of another monster oddball that will need a 300 gallon or bigger setup - a Hoplias lacerdae Wolf Fish that will, when it's fully grown, be around 30 inches in length and which will be capable (if anyone is stupid enough to put their arms within striking distance of couse!) of amputating a man's arm at the elbow. Not something you keep in the average living room aquarium.


Panda Catfish fan and keeper/breeder since Christmas 2002