Dead Cichlids

A little over a month ago, one of my wife’s friends from work gave her an enormous fish tank. I think it is 70 gallons, but I am not quite sure. It is 4 feet long, 15 inches deep, and 20 inches tall if that gives you any idea of the scale. To me, it is just fucking huge.

The fish tank came fully equipped, even including fish. The fish are African Cichlids (if you want to know what they look like google it. To me they look like Koi fish, but the also look like Goldfish, so I am not much of a judge). There were 13 of the guys that came along with the tank. Well, obviously not all guys, since many of them were the children of some of the other ones, and I don’t think they reproduce asexually (of course I don’t know, I didn’t actually pay any attention in biology class in high school.).

A couple of days ago, I was going to clean the tank for the first time. I wasn’t really sure what the proper procedure for cleaning was, so I just did like I do with our smaller tank, and started using a little gravity sucker thingy jobber to vacuum the crud off of the bottom. I began to remove all of the ornaments in the tank for cleaning purposes, and started to scrub the side with an aquarium brush (yes, I have three arms, which really made this a lot easier). While pulling the weeds faux foliage from the tank, I noticed a little baby fish, then another, then another… 14 in total. I decided that I had better put everything back the way it was, since I was not at all sure if Cichlids are the type that eat their own offspring, but I know that many species do.

So, how do I clean the tank without risking either the big fish eating the little fish, or sucking the little fish up in the gravity sucker thingy jobber? Two solutions. Solution in the first: Magnetic Aquarium Cleaners. This is a device I had never heard of, and it only cost about six bucks, but my god is it ever easy. Just two magnets with a scrubber on one, throw it in the tank, hold the other one outside of the glass and move it around just as if your hand was in the tank. I don’t know how I ever lived without it.

Solution in the second: A Plecostomus. I had wanted to get one when we initially got the tank, but couldn’t locate one large enough that there wouldn’t be a fear of the Cichlids eating it. I found one at PetSmart that was just about the same size as the Cichlids, so I was in business.

Time to leave the tank alone while the babies grow up.

The fish have been spending a lot of time near the top of the tank over the last few days. I had been attributing this to the temperature of the water, as the warmer the water, the less oxygen it will have in it. The tank still looked fairly clean from the gravity vacuum sucker thingy jobber I had used on it a few days ago. Although there was a bit of a fishy odor in the tank, but it is a fish tank, what do I expect? A friend called me on the phone at about six, and as I walked by the tank the fish were fine. I hung up the phone a little bit after seven, and as I walked past the tank again, about half of the fish were dead, and the ones that weren’t dead weren’t looking too chipper.

I didn’t know what the fuck could have happened to them so quickly. I could see if there wasn’t enough air in the tank maybe one of them would die, while the others started looking worse, but I was looking at about half the fish dead -in under an hour. The only thing I could think was that maybe the plecostomus had somehow gotten into, and clogged up, the filtration system. I yelled for the wife, and together we netted out the remaining fish. We put them into two buckets of clean water, one for the fish that still seemed pretty okay, one for the two of them that were barely clinging to life. Then we set about fishing out as many of the babies as we could -I think we got a total of 11 of the babies out of it, which is a pretty good total really, since I had only seen 8 since replacing all of the ornaments that day.

I started draining all of the water out of the tank with the gravity vacuum sucker thingy jobber as my wife put the baby fish into our smaller tank with the neon tetras (these babies are about the same size as the tetras). By now, the fish that had been on the verge of death only minutes before appeared to be back to normal. WHAT THE FUCK?

I continued to drain the water out of the tank with the gravity vacuum sucker thingy jobber, and was getting as much of the remaining crud out of the gravel as I went. When the tank was about 90% drained, I saw that Mr. Plecostomus was still in the tank, so there went my clogging up the filtration system theory -all of the large fish were now accounted for, and the baby fish were nowhere near large enough to cause a problem with it. That was when I saw what I am pretty sure was the problem: A tiny piece of broken glass. It looked like the bottom of a test tube.

As I continued to clean the bottom of the tank, I found the rest of the little glass thingy. It was a thermometer. Now my first thought was “mercury”, my second thought was “they haven’t used mercury in thermometers in decades”, my third thought was “Perhaps the internet knows the answer.”

The internet tells me that glass thermometers used in fish tanks are filled with alcohol (which makes sense since alcohol doesn’t condensate, otherwise there would be cloudy bubbles all over it all the time), which is toxic to fish. In addition to a liquid toxin in the liquid tank there are also little gray pebbles to weight the thermometer down. Some websites I found say that they are toxic while others say they are harmless. In my case the little gray pebbles weren’t spilled, so it wasn’t really an issue anyway. I didn’t even know we had a thermometer in the fish tank, I hadn’t seen it in the month+ that we have had it, but what are you gonna do.

Unfortunately, there are as many opinions on the best course of action now as there are forums. Some say that you should scrub everything with bleach and replace it, which I am most certainly not going to do, since the bleach residue is at least as harmful as the alcohol. Some say that you should only change half of the water, wait a few days, then do it again. Some sites that you should remove only a small portion of the water, and put a carbon filter cartridge in the tank to absorb the remaining toxins. There is certainly no lack of answers. Alas, I have no way of knowing whether Fishmanfl32 or bettababe have a better working knowledge of marine biology, so I am gonna just have to wing it.

I settled on replacing all of the water, and cleaning the gravel only using the gravity vacuum sucker thingy jobber. One of the forum posts that I read said that you don’t want to sterilize all of the ornaments and gravel because they contain bacteria necessary to break down the fecal matter that the fish produce. I am all about something other than me breaking down fecal matter, so I am going to give that approach a try. The fish seemed to spring right back to life once they were out of the contaminated water (well that was a poor choice of words, the ones that were already dead are still very much dead, but the ones that were nearly dead are now bright and chipper). So I hope that changing the water and cleaning the gravel as best I could with the gravity vacuum sucker thing jobber does the trick.

I will probably post with the results in a few days, since I wasn’t able to find any listings of people who had experienced this problem. Well, that is, I wasn’t able to find anyone posting results after attempting the suggestions. If this one works, I will let you know. That way the next time someone googles for dead fish aquarium broken thermometer they will at least know the results of trying it my way.

If you ever happen to google for gravity vacuum sucker thingy jobber, you will probably end up here as well, but that is totally unrelated.


Two days have now passed since the onset of the problem, and I can say with certainty that changing the water and vacuuming the gravel was sufficient to get rid of the toxins. I went to a pet store yesterday to see exactly what was in one of those thermometers, and found that the little pebbles in it are in fact lead. Why on earth do they manufacture something for an aquarium that has alcohol and lead, both toxic to fish, in it? And why on earth would anyone actually put one into their aquarium? To those questions, I have no answers.

A note on changing the water: Our aquarium is set up so that the entire length of the back of it is actually a water filter. The pump pulls water from the top on the left and cycles it through a series of spiky balls and filters before eventually being pumped back into the tank on the right. To remove as much of the contaminated water (and miscellaneous junk) as possible, when I began to fill the tank, I did so with the filter turned off and started filling in the filter system itself. The way our tank is set up, this forced the water to run backwards through the filter system to eventually overflow into the main tank, where I vacuumed all the crud out of it. I left the water running at just about the same speed as the vacuum was able to pull it out, and continued that process for over an hour. By the time it was done, the water that was flowing out of the filter system was all completely clear. I am not sure if that was entirely necessary just to remedy the contaminated water problem, but it did leave the water a lot purer than it otherwise would have been. As anyone who owns an aquarium knows, clear water is sure a lot prettier/healthier than scuzzy water.

The fish that survived the initial shock are now back to moving and playing like they have not done since we first got the tank. This leads me to believe that there may have been other mitigating factors which caused the sudden deaths. While I am sure the alcohol was the actual killer, I am thinking there was probably a problem with the pH or something else that was pre-existing. That is something that I have never worried about with a smaller tank, since the fish only cost a buck and when they die, they die -not that I would intentionally let them die. I suppose I probably should buy a test kit to monitor the pH and nitrates and the such so that I can avoid a repeat of this.

In other fish news, the baby fish are doing quite well in the 20 gallon tank with the little tetras. As I said previously, they are roughly the same size as the tetras, but they are quite obviously babies. You can still see through parts of them, and I don’t think they have even grown full sets of scales yet, but they are buzzing along just like the rest of the fish in the smaller tank. And boy is it ever cute to watch them eat -which is something I had not thought of until we had the problem with the large tank. The little guys are perfectly capable of eating the tropical flakes that go into the small tank, but I am not quite so sure if they would have been able to eat the large pebbles that we feed the adult Cichlids.

So, while we did lose half of the adult Cichlids in the thermometer break incident, we actually came out with more fish because of it. I have no doubt that many of the baby fish would have died in the large tank, either from lack of food (mouths too small to eat the pebbles) or the larger fish eating them. Now that they are in the smaller tank, we plan to leave them there until they are large enough to fend for themselves in the big tank. Since 11 of them made it through the toxic water (one even survived fifteen seconds or so on the kitchen stove -that was how we found out that the net has a hole in it), I don’t see why all 11 of them can’t grow to full size. So, strictly by the numbers, we started with 13 of them, we should end up with 17 of them.

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