3 Fish dead in 1 month... What am I doing wrong!

Hi, about 5 minutes ago I look over at my tank to see that there is a fish laying on the floor. Strange thing I though, but until I walked up to the tank I didn't realize what what actually going on. A fish that was perfectly fine about an hour or two ago was laying dead on the floor. This is the third fish this month.

Here's the timeline:
December 7th: I posted this thread, https://www.fishforums.net/threads/fish-has-white-spots-and-is-dying-day-4.466515/ outlining the sudden illness that came down on the first fish and I lost him only 4 days later. This fish was completely fine up until the day it happened, within hours of seeing him this problem developed. Insanely quickly with little to no evidence of another problem. Normal swimming, eating, poo looking fine, etc. I continued to watch his/her tank mates constantly looking for any sign something was wrong and I saw nothing. Nothing until December 24th.

December 24th: I posted this thread, https://www.fishforums.net/threads/...ng-and-rapidly-breathing.466944/#post-3998289 explaining the problem with my fish that was euthanized January 4th, when it was decided it was the only thing that could be done to help it. A very hard thing to do but the best thing for her. She had always been kind of fat since the day I brought her home, which was assumed to be caused by pregnancy. I later discovered after help from the forum post that it was likely an infection. I began treatment but it had been to late. I continued with the medication to make sure that if it had spread to the others it would be dealt with, even though they had none of the early signs of a parasite. The treatment was started on the forth and ended on the 7th. I used API First Cure for Parasitic Infections. Still to this day none of the fish were visually infected.

January 8-9th (Today as of making this post): At about 12 midnight, I found the third victim of this killer. Upon examination, there were no signs of parasites that I know of, but the fishes gills were slightly flakey, like the skin on dry lips. Up until the loss, the fish was slightly lethargic but not to the point were I was thinking there was a problem. Other than that, he was swimming less often but still normal, eating normally and pooping normal.

As of currently there is one fish in the tank and an algae eater. The fish I lost on the 11th of December, the one I lost on the 4th of January and the one currently living were/are all about 8 months old, the aquarium they've been in is about 9 months old, and they are all sunburst platies. The one I lost today is over a year and a half old, and has lived in the tank for the same amount of time as the others, about 8 months, and was a sunburst platy. The algae eater is at least 4 years old (can't really remember) and has been in the tank as long as the others. I also had a few live plants in the tank but removed them as they were dying because I don't really have the right tank for them but still have a living java fern and a ribbon. One notable thing is that I've been having an influx of algae so i have reduced the light levels to try and decrease that problem.

TANK STATS (Measured in mg/L when possible)
Ammonia: 0ppm
Nitrite: 0ppm
Nitrate: 0-5ppm
pH: 7
Temp: 75-77 but mostly stays at 77 (Fahrenheit)
KH: 80ppm
GH: 180ppm
29 gallon tank with heater and HOB filter (Using filter cartages)
Medium sized airstone in the back of the aquarium
Please request any other needed info!

This has been of course a very traumatizing experience that went from a death to a very strange coincidence to a big full aquarium problem. The current fish is very energetic and always has been. Swimming around, eating normal and pooping a normal color. However, that's what happened to two of the other fish and now they have passed away. I'm clearly concerned by whatever is happening to these fish and I need to get to the problem and fix it. Any info will help, any recommendations are welcome, and any solutions or ideas of the problem are greatly appreciated. With any needed info please make a comment and I will get back to you as soon as possible. Thanks.

The first platy looked like it had been attacked by something.
The second platy probably had an internal protozoan infection.

What sort of algae eater do you have?

How often do you do water changes and how much do you change?
Do you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before adding it to the tank?

How often and how do you clean the filter?

How often do you feed the fish and what do you feed them?

What other fish are in the tank?
Can we get a picture and video of the tank and the remaining fish?

Have you dewormed the fish?

Do you have buckets, sponges, etc specifically for the fish tank, or do you use any bucket from around the house?
Do you have cream, grease, oil or anything on your hands when you feed or work in the tank?
Do you use anti-bacterial soap to wash your hands?
Does anyone smoke, use paint, hair spray, perfume, deodorant, air freshener, etc, in the room with the tank?

Hi, here's some answers
The type of algae eater, I'm not sure but I will attach an image of him if that helps.

I do a 33% water change weekly and a 50% monthly, I clean the gravel with a gravel vacuum every water change, and I use aquasafe+ from tetra for dechlorination before adding the new water to the tank. I replace the filter monthly with the 50% water change.

The fish are fed with Tetra flakes and the algae eater with algae wafers all of which is done once a day.

The only things in the tank as of currently are the sunburst platy and the algae eater, I'll link a picture below and try to get a video below.

The fish have not been dewormed but I do have deworming powder if you want me to start that prosses.

I use a 5g bucket for the fish tank exclusively, a wall scraper sponge for them exclusively, other than that, I do have the gravel vacuum.

I clean my hands before feeding and I always clean my hands and arms with hot water and soap before working in the tank. I never have any product of any kind on them.

I don't smoke, paining is done outside when I do paint, I don't use anything of the things on that list whilst in the fish room.

Hope all of this helps, if you have any more questions or I didn't answer one of them right please ask and I will respond as soon as possible.


I wasn't able to post a video but if there's a way I can better send it please tell me!

Do you have a photo of the algae eater?

I added the picture to the main post.

Ah I see it now. it's a chinese algae eater aka sucking loach.

Colin commented that the first platy looked like it had been attacked by something - the chinese algae eater is #1 suspect for this.

He's always been quite skittish, but as he's gotten older he's been less afraid. There's a small cave in the coral structure he likes to sit in and doesn't mind when other fish are next to him. However an attack from him I guess is quite likely. He used to live in a 10g tank because that's what the pet store recommended but he moved into the 29g with the others when I put them in. But now that I'm reading this it looks like it needs a much bigger space... He's currently about 5.5 inches long and still growing slowly.

The easiest way to put videos on this forum is to upload the video to YouTube, and then copy & paste the link here. We can view it at YouTube.

If you are using a mobile phone to take the video, hold the phone horizontal so the video takes up the entire screen. If you have the phone vertical, you get video in the middle and black on either side.

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Neleono said:

I replace the filter monthly with the 50% water change.

Click to expand...

Do you clean the filter media/ materials or actually throw the old bits out and put new bits in?

You don't want to replace filter media unless it is breaking down. When you throw the old filter media away, you get rid of the good bacteria living in it and this can cause ammonia or nitrite problems in the water.

If your filter has pads/ cartridges that "need to be replaced each month", replace them with a sponge from another brand of filter and the sponge will last for years. If you do want to add a sponge, don't replace all the media at the same time. Add the sponge and wait a month, then remove one of the filter pads. Add some more sponge, wait another month and then remove any remaining pads/ cartridges.

Sponges and most other filter media can be washed out in a bucket of tank water and re-used. The bucket of dirty water gets poured on the lawn/ garden and the tank gets topped up with clean dechlorinated water.

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Livebearers like platies, guppies, swordtails and mollies regularly have intestinal worms but you can check the fish for possible signs of infection. Look at the platy's poop, if it's white and stringy, and the fish is eating well, then it probably has intestinal worms. If the poop is coloured, then it might have a few worms but not enough to warrant treating the tank.

If/ when this problem is resolved and you add more fish, you could deworm the tank then so you deworm a lot of fish, rather than just two fish.

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Neleono said:

I clean my hands before feeding and I always clean my hands and arms with hot water and soap before working in the tank. I never have any product of any kind on them.

Click to expand...

Does the soap have any perfumes or anti-bacterial substances in it?
If so, this can cause problems in aquariums. Most anti-bacterial soaps and soaps with perfumes, can leave a residue on your skin and this can wash off in the tank water and poison the fish.

Unless you have grease, cream or something else on your hands, it is best to just rinse your hands and arms under water before working in the tank.
Use warm soapy water after working in the tank.

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A 5 inch Chinese Algae Eater is just starting to reach maturity and will be an issue later on when it gets bigger. They regularly hit 8 inches and I have seen them 12 inches long. They get more aggressive and territorial as they get older.

I wouldn't put it past the algae eater to attack other fish in the tank at night when they sleep, or if they go near his hiding place. Chinese Algae Eaters will also attack and eat sick fish.

Unless you have a close attachment to the algae eater, I would probably rehome it with some much bigger tougher fish or leave it on its own.

So if I don't get rid of the algae eater it will me a threat to my tank and possibly cause injury or death to what I put into the tank...

Possibly. Most Chinese Algae Eaters cause problems when they get bigger. When I first started in the pet industry we had customers bringing them back every week because they attacked everything. Eventually we stopped carrying them or only sold them to people that kept big boisterous fishes like cichlids and large barbs.

There are plenty of other smaller more peaceful algae eating fishes if you want one.

Are there any fish that would be good in a 29 gal tank that would be safe or is giving away my only option

trade it in for some credit at a pet shop