# Looking for help with a weird problem. \[Disappearing aquarium fish apparently reappearing later\] **URL:** \ **Category:** Factual Questions\ **Created:** [October 18, 2010, 4:27am UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531 "2010-10-18T04:27:30Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![strangeluck2010](https://avatars.discourse-cdn.com/v4/letter/s/439d5e/32.png) [@strangeluck2010](https://boards.straightdope.com/u/strangeluck2010)\ **Post date:** [October 18, 2010, 4:27am UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/1 "2010-10-18T04:27:30Z")
You may not be the people to help me but you might know who could. First of all let me start by saying this isn’t a joke. It is a really happening: I purchased a brand new 6.5 gallon round (round means cylinder shaped, not globe shaped) fresh aquarium for my then three year old daughter. We got a half dozen glow fish in yellow, orange and pink. and two tigers and two small crabs. Over a few month period we had a couple glows and one tiger die. I netted the actual floaters. Nothing mysterious there, I would assume, just natural causes. These were replaced with new fish. Until that is the weirdness started – One morning a fish was missing. I don’t remember what color but it was a Glow. We assumed that the crabs had scavenged the body. This had happened to a minor degree with those dead fish in the past. So, we now had five glows and two tiger fish. A few days later I replaced the glow with a new one. that puts back a six glows. A COUPLE weeks later we have SEVEN glows. All full grown – no babies. Over time one of the tigers disappeared for several days and came back. More of the glows would disappear and then eventually return. One of the tiger fish died – body to prove it! – and we didn’t replace him. It got to the point that I didn’t buy more fish to replace the ones that went missing because I never knew if the things would “pop back”. A couple weeks ago our count was four glows (three orange, one yellow), one tiger and one crab (the second crab died of natural causes – body to prove it – one morning we found only two glows (two orange), one tiger and one crab. Yesterday there were three glows (all orange), one tiger and one crab. Today there are four glows (three orange and one yellow), one tiger and one crab. I know this whole thing sounds like a hoax. It’s not. They disappear and then they reappear. Someone may say that because the tank is round it forms an optical illusion – a blind spot – it does, I agree to that. But the fish only “hide” in that blind spot for a minute or two at most. The crab can use that trick for a few hours if he takes a nap back there. but that doesn’t account for the two times I have had fish disappear, I clean the tank down to empty plastic cylinder and then the fish return days or weeks later. Someone may say that a person in my household is playing a little game. Living at my house are my now four year old daughter – she has the sense of humor for it but is incapable of pulling it off as a stunt. My wife doesn’t have the time or that kind of sense of humor. My 67 year old mother isn’t really the type either. I’ve questioned everybody pretty hard and they are as lost about the whole thing as I am. I know it sounds nuts, but I wanted to start here before I go to some paranormal website. I already feel like a complete kook. Anybody got anything for me? Please? ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [October 18, 2010, 4:36am UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/2 "2010-10-18T04:36:23Z")
I know nothing of fish keeping, so I’ll start with the obvious. Is there anywhere for them to hide? You said the tank has a blind spot, but can they hide inside or behind any decorations or equipment? Also, I’d suggest you pay (closer) attention to which color fish is missing. I wonder if it’s possible that each time you count and find yourself down one fish, that it’s a different one missing and you just don’t realize it. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 18, 2010, 5:59am UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/3 "2010-10-18T05:59:15Z")
There are really only three possibilities. 1. The fish are somehow hiding somewhere in the tank. However, you say you have sometimes drained the tank entirely and not been able to find the missing fish. 2. Someone is playing tricks on you. If it isn’t a member of the household, perhaps they are letting in a relative or friend who is the one playing the trick. If #1 is eliminated, then this is probably the case. 3. You’re counting wrong or have some kind of perceptual problem that is causing you to confuse the numbers of fish. PS. I have edited the title to indicate the subject. ---
**Author:** ![Rigamarole](https://avatars.discourse-cdn.com/v4/letter/r/77aa72/32.png) [@Rigamarole](https://boards.straightdope.com/u/Rigamarole)\ **Post date:** [October 18, 2010, 4:02pm UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/4 "2010-10-18T16:02:05Z")
> [@Colibri](#): > > There are really only three possibilities. > > 1. The fish are somehow hiding somewhere in the tank. However, you say you have sometimes drained the tank entirely and not been able to find the missing fish. > > 2. Someone is playing tricks on you. If it isn’t a member of the household, perhaps they are letting in a relative or friend who is the one playing the trick. If #1 is eliminated, then this is probably the case. > > 3. You’re counting wrong or have some kind of perceptual problem that is causing you to confuse the numbers of fish. You forgot: 1. The fish are warping in from _another dimension_. Contact the Ghostbusters immediately. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 18, 2010, 4:28pm UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/5 "2010-10-18T16:28:14Z")
> [@Rigamarole](#): > > You forgot: > > 1. The fish are warping in from _another dimension_. Contact the Ghostbusters immediately. Another possibility is that he has been purchasing the fish from the [Heisenberg Pet and Aquarium Centre.](http://search.insing.com/business/heisenberg-pet-aquarium-centre/serangoon/id-bc840000)🙂 This may also be a real-life example of [Paul Dirac’s solution to the classic fisherman puzzle:](http://motls.blogspot.com/2009/08/paul-dirac-birthday.html) > [@](#): > > Three fishermen catch N fish. In the morning, one of them wakes up. He fairly wants to take 1/3 of them and leave. But the number is not a multiple of three, so he throws one fish back to the pond and takes 1/3 of the rest. > > The second fisherman doesn’t know that one of his colleagues is already gone. Once he wakes up, he also wants to take 1/3, but the fish ensemble he sees is not a multiple of three, so he throws one fish away and takes 1/3 of the rest. > > The third fisherman doesn’t know that they’re gone, so he throws one fish and takes 1/3 of the rest, too. What’s the minimum number of fish N that they had to catch? > > The clever classmates of Dirac found the conventional answer, 25. (25-1 = 24, 24-8 = 16, 16-1 = 15, 15-5=10, 10-1=9, 9-3 = 6). However, Dirac was better because he found a smaller solution. Of course, the fisherman caught N=-2 fish (-2-1 = -3, -3-(-1) = -2, and so on). The advantage of N=-2 is that it is a fixed point. (Other solutions differ by multiples of 27.) Evidently there are a couple of negative fish swimming around in the tank. ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [October 18, 2010, 4:34pm UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/6 "2010-10-18T16:34:41Z")
What kind of substrate are you using at the bottom of your tank? My first thought is that they might be hanging out dug in, so to speak. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 18, 2010, 4:45pm UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/7 "2010-10-18T16:45:12Z")
> [@wevets](#): > > What kind of substrate are you using at the bottom of your tank? My first thought is that they might be hanging out dug in, so to speak. Unlikely in the case of the [GloFish](http://en.wikipedia.org/wiki/Glofish), which are genetically modified zebrafish and which would be very unlikely to burrow. ---
**Author:** ![jjimm](https://avatars.discourse-cdn.com/v4/letter/j/ba8739/32.png) [@jjimm](https://boards.straightdope.com/u/jjimm)\ **Post date:** [October 18, 2010, 4:48pm UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/8 "2010-10-18T16:48:15Z")
Whatever the explanation, I suggest you a) photograph the tank every day, b) count the fish from the photograph, and c) log the relative fish numbers in a spreadsheet. Follow the pattern for a couple of weeks. ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [October 18, 2010, 4:53pm UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/9 "2010-10-18T16:53:22Z")
What kind of pump/filter are you using? Is it possible the fish are getting caught in in there somehow? By the way, that seems like a lot of animals for such a small tank, and cleaning it all the way down to the bare tank is not good for maintaining the bacterial colonies that help to manage ammonia levels. ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [October 18, 2010, 5:06pm UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/10 "2010-10-18T17:06:34Z")
> [@Colibri](#): > > Unlikely in the case of the [GloFish](http://en.wikipedia.org/wiki/Glofish), which are genetically modified zebrafish and which would be very unlikely to burrow. That’s neat. I had no idea those guys were on the pet market. They look like they’d be easy to find unless something is blocking them from view. ---
**Author:** ![TruCelt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/trucelt/32/523_2.png) [@TruCelt](https://boards.straightdope.com/u/TruCelt)\ **Post date:** [October 18, 2010, 5:31pm UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/11 "2010-10-18T17:31:22Z")
They are almost certainly hiding/stuck in the filter. Fish are constantly hanging out in there and then reappearing. It’s also possible to have babies which grow to a fairly large size before leaving the filter. Any that come out too soon will likely get eaten. Needless to say you are also quite overstocked. I hope you are changing in the neighborhood of 50% water each week. It’s completely unneccesary, and quite stressful for the fish to be taking all the water out like that. Just get a Python [http://www.amazon.com/50ft-Python-Spill-Clean-Fill/dp/B000255NXM/ref=sr\_1\_1?s=home-garden&ie=UTF8&qid=1287422782&sr=1-1](http://www.amazon.com/50ft-Python-Spill-Clean-Fill/dp/B000255NXM/ref=sr_1_1?s=home-garden&ie=UTF8&qid=1287422782&sr=1-1) and some good water conditioner (my favorite is Prime [http://www.amazon.com/Seachem-436-Prime-250ml/dp/B0002568S6/ref=sr\_1\_16?s=home-garden&ie=UTF8&qid=1287422843&sr=1-16](http://www.amazon.com/Seachem-436-Prime-250ml/dp/B0002568S6/ref=sr_1_16?s=home-garden&ie=UTF8&qid=1287422843&sr=1-16) ) A great resource for aquarium info is [Badmanstropicalfish.com](http://Badmanstropicalfish.com) (forums at: [http://www.badmanstropicalfish.com/forum/index.php](http://www.badmanstropicalfish.com/forum/index.php) but tool around a bit first, you may find the answers you need already posted. And tell them that TruCelt sent you 😉 ---
**Author:** ![kayaker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayaker/32/441_2.png) [@kayaker](https://boards.straightdope.com/u/kayaker)\ **Post date:** [October 18, 2010, 5:46pm UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/12 "2010-10-18T17:46:52Z")
I have seen fish get into the filter (in the tank, or external) then later get back out. ---
**Author:** ![Rhodes](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rhodes/32/273_2.png) [@Rhodes](https://boards.straightdope.com/u/Rhodes)\ **Post date:** [October 18, 2010, 9:18pm UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/13 "2010-10-18T21:18:37Z")
I had exactly the same problem. One disappeared for months. Sometimes they’d burrow into the gravel, but the really sneaky ones were found in the little reservoir inside the filter. ---
**Author:** ![ataraxy22](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ataraxy22/32/307_2.png) [@ataraxy22](https://boards.straightdope.com/u/ataraxy22)\ **Post date:** [October 19, 2010, 1:56am UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/14 "2010-10-19T01:56:33Z")
I had a kuhli loach once that disappeared for 6 months before reappearing in a 20 gallon tank. ---
**Author:** ![gladtobeblazed](https://avatars.discourse-cdn.com/v4/letter/g/85f322/32.png) [@gladtobeblazed](https://boards.straightdope.com/u/gladtobeblazed)\ **Post date:** [October 19, 2010, 2:10am UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/15 "2010-10-19T02:10:10Z")
I once had an eel that burrowed into the gravel as soon as I put it in the tank. I saw it maybe twice in an 18 month period. What a waste of money. ---
**Author:** ![Looey](https://avatars.discourse-cdn.com/v4/letter/l/ee7513/32.png) [@Looey](https://boards.straightdope.com/u/Looey)\ **Post date:** [October 19, 2010, 2:12am UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/16 "2010-10-19T02:12:38Z")
Is your filter the kind that a fish could get stuck in (hangs on the outside of the tank)? Have you thied to position yourself to look directly down into the tank instead of through the curved surface? ---
**Author:** ![TruCelt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/trucelt/32/523_2.png) [@TruCelt](https://boards.straightdope.com/u/TruCelt)\ **Post date:** [October 19, 2010, 10:05am UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/17 "2010-10-19T10:05:47Z")
> [@gladtobeblazed](#): > > I once had an eel that burrowed into the gravel as soon as I put it in the tank. I saw it maybe twice in an 18 month period. What a waste of money. LOL! I can’t tell you how many times I’ve held last rites for my Horsehead loaches. Once they disappeared about 8 months before I moved. I had completely emptied the tank and was scooping out the gravel when I heard a movement - scared the bejeezus outta me! LOL! Damn things, they were both in there, and I had to go through every pebble of a highly planted 100 gallon tank by hand in order to find the second one. That second little bastard was _already in the scoop bucket_! ! ! They still appear occasionally, especially if I drop in some mysis shrimp. ---
**Author:** ![Sycorax](https://avatars.discourse-cdn.com/v4/letter/s/a4c791/32.png) [@Sycorax](https://boards.straightdope.com/u/Sycorax)\ **Post date:** [October 20, 2010, 12:18am UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/18 "2010-10-20T00:18:10Z")
The filter is a possibility, although I thought tanks that small used under-gravel filters. Could the crab be the culprit? I had a blue crayfish once who dined on a snail and a few fish before I figured out what was happening (and saw the cray trying to catch a fish). Couldn’t a crab get a fish? I want to add my voice to those who said the tank is too small. Yeah, you can do frequent, partial water changes, but it’d be better to get a bigger tank; 10-gallon minimum; 20-gallon better. And with a 20-gallon, you could add one or two more fish. Please do check out some websites for help in establishing and maintaining a healthy tank. Good luck. ---
**Author:** ![BoBettie](https://avatars.discourse-cdn.com/v4/letter/b/4af34b/32.png) [@BoBettie](https://boards.straightdope.com/u/BoBettie)\ **Post date:** [October 20, 2010, 2:47am UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/19 "2010-10-20T02:47:21Z")
Wait until your crabs “die” and you scoop out their apparently dead bodies…and weeks later there’s a NEW CRAB. Turns out the perfectly intact dead crab looking shell I scooped was a molt from my crab and he was hiding in a tiny part of a decoration growing his new exoskeleton. I about crapped my pants when he fell out of there during a tank cleaning. I’m betting they’re burying in the substrate. There’s no other explanation. ---
**Author:** ![Cheshire\_Human](https://avatars.discourse-cdn.com/v4/letter/c/5f8ce5/32.png) [@Cheshire\_Human](https://boards.straightdope.com/u/Cheshire_Human)\ **Post date:** [October 20, 2010, 1:00pm UTC](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531/20 "2010-10-20T13:00:49Z")
The obvious solution to this problem is that [_ **Schrödinger’s cat** _](http://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat) has taken up residence in your house. Being in a superposed state, he can come and go as he pleases without being seen, until Schrödinger finishes the damned experiment, collapses his wave function, and reveals his state, either dead or alive. The cat is actually _ **eating** _ the fish, whereupon the fish take on his superposed state. In this superposed state, they have a very large [_ **de Broglie wavelength** _](http://en.wikipedia.org/wiki/De_Broglie_wavelength), which can, in minutes, days, or even years later, occasionally have their **ψ** [sup] **2** [/sup] functions overlap the [_ **Planck length** _](http://en.wikipedia.org/wiki/Planck_length) of the original fish tank. Whereupon they “POP” back into a real existence. I got this explanation watching the latest _ **Star Trek** _ episode, so it must be true. [Next page](https://boards.straightdope.com/t/looking-for-help-with-a-weird-problem-disappearing-aquarium-fish-apparently-reappearing-later/557531.md?page=2)