dying fish- no symptoms

[staceyv]

I have a 20 gallon high tank.Last week, I HAD 2 small mollies, 3 small swordtails, 6 neons, 2 small danios, and about 10 guppies. I also have a 4 inch long pleco. I have had this fish tank for 7 years. I recently had just a pair of convicts in it with the pleco. The big male died one day (about 3 weeks ago)- his stomach was very swollen and it seemed to happen overnight. the female had a few scratches on her side. I gave the female convict away and restocked my tank with all of the above fish (5 days ago).
In the last five days, here's what happened. Overnight, the male swordtail died. he was never active from the beginning- he just sat on the gravel. Then, two guppies died that day. Over the next few days, the fish were active and healthy. I even had lots of tiny baby guppies swimming around. After the 3 fish died, I had my water tested at the pet store- No ammonia, no nitrates, neutral ph, high levels of good bacteria.
i did a 2 1/2 gallon water change one day and another 2 1/2 gallons the next day. i changed the carbon in the filter(and rinsed it first), and i rinsed the foam sponge part in a bucket of fish tank water (to preserve good bacteria). I am using an Aquaclear 200 for filtration. i also added freshwater aquarium salt as directed on the package (it said guppies thrive on it) and i used "Stress Coat" to dechlorinate the water. The water i added was 78 degrees, just like the water in the tank. i also added some sodium phosphate to lower the ph and a tiny bit of sodium bicarbonate to raise it to a perfect neutral. Today, i found a dead guppy (one of the new ones) and a dead female swordtail. Also, one of my neons is gone. He must have died too, and gotten eaten or sucked up by the filter. i don't see any babies in there anymore. the remaining fish are swimming around normally, eating normally, etc. they look 100% healthy.

I have NEVER had a problem like this in 7 years. these fish that are dying look and act 100% healthy and normal until all of a sudden, they're dead. They don't have any bite wounds or scratches. They aren't bloated...no ick... I have not added any decorations to the tank.
I have not used any cleaning solutions around the tank, and i don't stick my hands in the water unless i know they are free of lotion, etc. My algae eater has been in this tank for 6 months and he's fine. Some of the guppies in this tank have been in there for 3 months-they were feeders that the convicts never ate. Thay are fine too. What's going on?
Do algae eaters kill fish?
Is the disease or affliction that killed my male convict killing these fish- and if so, why would all of these guppies and pleco be fine, and why would they be breeding?
Did i just buy a bunch of sick fish?
please give me some insight!

 

[LittlePuff]

How long have you been using the chemicals to adjust your Ph?

Kim

 

[Menagerie]

In the last five days, here's what happened. Overnight, the male swordtail died. he was never active from the beginning- he just sat on the gravel. Then, two guppies died that day. Over the next few days, the fish were active and healthy. I even had lots of tiny baby guppies swimming around.

Females can give birth right before dieing--it is a way to keep the species going. This is not a sign of health.
Did you get all these fish at the same LFS? Did anything seem odd in their tanks? How long was the tank empty or have few fish before all of these fish were added?

i also added some sodium phosphate to lower the ph and a tiny bit of sodium bicarbonate to raise it to a perfect neutral.

A steady pH is better than perfect. All these fish will do well from 6.7-7.6 or so. What is the pH of your tap water? Allow the tap water to sit out over night, or for 8 hours in a cup to let the gases equilibrate and then test the water.

After the 3 fish died, I had my water tested at the pet store- No ammonia, no nitrates, neutral ph, high levels of good bacteria.

Are you sure they tested for nitrAtes and not nitrItes? NitrItes are deadly to fish, nitrAtes are plant fertilizer and tolerated to 40ppm by most fish. If they didn't test nitrItes, have them run that test and pick up your own water test kits while you are there How do you know there is a high level of good bacteria?

Do algae eaters kill fish?

If you are talking about the pleco, I don't think that is causing this problem.

Answer these Qs and then I will give you some websites to look at depending on where the answers point. In the meantime, do a 25% water change and do not clean the filter pad.

 

[staceyv]

to answer kim's question, i've been using the same chemicals to adjust the ph for 7 years. (i've had to buy refills, but not in the last 6 months or so).

to answer menagerie: 1)yes, i got all of the fish at the same pet store.
they had floaters in 30-40% of the tanks, but i worked there years ago, and that was about normal.
2)the tank had two large convicts, a 4 inch pleco and 8 or 9 guppies for months. the male convict died awhile ago, so i had the others left up until the same day i bought the new fish.
3) my tank always has a steady ph. i made the tap water match the ph of the water i had in the tank (which was neutral). the tap water here is very very alkaline.
4) maybe they tested for nitrites. they both sound the same to me! she tested a bunch of stuff, it was a strip with about 6 or 7 different values on it.
by looking at those values, she concluded somehow that i have high good bacteria and low to zero bad bacteria. it was the owner of the store who tested the water. she owns about 15 tanks herself. i'm pretty sure she must know what she's talking about.

 

[Menagerie]

i'm pretty sure she must know what she's talking about.

Then she should know liquid tests are more reliable than strips

the tank had two large convicts, a 4 inch pleco and 8 or 9 guppies for months. the male convict died awhile ago, so i had the others left up until the same day i bought the new fish.

Okay, I was wondering if the addition of those fish was too much for the bacteria to handle.

I don't think this is illness, but stress. Do you know if that LFS quarantines incoming fish? Shipment is very stressful on fish, they get to the store, sit there and then get moved to your house. What is the LFS' "stay alive" policy. Good LFSs have one because they know that fish may die within the first few days of going to a new tank with no outward signs of illness. For example, one of the LFS around here allows you to bring in dead fish plus a separate water sample for 15 for full credit. If the water sample tests fine, credit is issued. From 16-30 days, you get half credit. I always QT fish for two weeks. If they die, they go back to the store so I can get new ones.

 

[staceyv]

I found another dead fish today, and one of the fish has a white cloud on it's tail- (on it's body, not on the fin.) it's not ick. it's got to be either bacterial or fungal. none of the other fish that were dying had any outward signs of illness, but now this...i just thought of something- i'm pretty sure my male convict died of dropsy, because he was completely swollen and he looked like a pinecone. that's a bacterial infection. it's not supposed to very very infectious, though. my tank is just obviously very accomodating to bacteria and fungus. Should i really change the gravel every year? and how often should i do water changes, because for the last seven years, i've only changed 1/8 to 1/4 of the water every 3-4 months( and 75% three times when i moved), without ever having any problems...maybe these damn feeder guppies introduced all of this bacteria??
i just want to get rid of all these sickly and plain looking fish, and fill the tank with baby africans, but i want to make sure my water's good first, without having to recycle the tank. i also want to keep my pleco alive!! any suggestions?

 

[andrewhuynh265]

that is the EXACT same thing that happened to me. my mail swoard tal and 2 guppies died the day and the day after i got them. they didn't have ich or anything because theres no spots, but the only thing that i could see that was wrong was that they kept swimming at the top, but it wasn't like all over the place. they were just at the top.

 

[frshwaterfinatc]

I've had crazy things like that happen in the past. And I blame weather changes when nothing else can explain it. Honestly, if I can feel humidity/pressure changes in the air from day to day or during a storm or before seasons change, then fish must be able to as well. Once the weather here suddenly cooled from the weeks-long 90 degree weather to mid 50's and 60's, eight of my seventeen bettas died overnight for no apparent reason. They were fine at night, the thermostat was set, and yet the pressure/humidity change must have still affected them. I feel for you. I'm so sorry about your losses. And I do hope things take a turn for the better.

 

[Menagerie]

maybe these darn feeder guppies introduced all of this bacteria??

They may have, but you also introduced a bunch of fish all at once without QTing.
Do you have a QT tank to separate out ill fish. Did you find out what your LFS' stay alive policy is? Is the LFS also battling fungal or bacterial growth?

fill the tank with baby africans

With a 20 gallon tank, what speicies are you considering?

 

[staceyv]

i want the smaller lake malawi cichlids. They are usually the cheaper and easier to find variety. I used to keep them, and i loved it when they bred!! The female used to hold all of the babies in her mouth, spit them out and suck them back in if she sensed danger. i really liked them. They died off over the course of the years, and i was left with my convicts, who were alive and well in the brackish water.(it's all freshwater now). The only major troubles i've ever had with my aquarium were right at the beginning with new tank syndrome, and now this with these community fish. I should stick with what i've had the most luck with! One big question: Can i even keep my pleco in brackish water, or would i need to acclimate the africans to freshwater?

 

[Menagerie]

Can i even keep my pleco in brackish water, or would i need to acclimate the africans to freshwater?

Plecos are FW fish, as are all cichlids. I'm surprised the convicts did well. BTW~Convicts are American cichlids.
Which small Lake Malawi species are you referring to?