Livebearers dying one by one - help needed

[ramanan]

I am losing 1 or 2 fish every day since 3 three weeks.
All are live bearers (Platies, Swordtails and mollies). I have shrimps, plecos and unwanted pest snails in my tank
Also have plants and drift woods. One of the drift wood is from eucalyptus which was there for more than 2 months.
Other than livebearer fish nothing seems affected. It looks like something to do with livebearer fish

Symptoms starts
1. Fish is inactive staying in one place. Especially near the filter. Otherwise Swimming well. Not wobbly or wired swimming behaviour
2. Stopped eating even when favourite flakes added
3. then string of white poop. Attached to fish for long time
4. Dead after 1 or 2 days at bottom. Some twitch and stays in the bottom then die

Checked my water with local petbarn and the water PH, Nitrite and Nitrate are in safe level
Added Aqua One broadspectrum remedy but it is not helping much.
Any advise is much appreciated


more information:

How long have they been there? I have this Aquarium since last December 2025. This issue started in last 3 weeks. Before all was healthy and there are about 20 fries

- What is the diet? Vipan Fish flakes, and fish pellets from local fish store. Also I add little bit garlic paste then and there. Because there was white spots on new came. Now those are gone. I also started Seachem Nourish

- Is there -any- discolouration on the body (especially white patches on/between scales and mouth? Not at all. The couple of new fish had white spots but that's all cured after little bit garlic and API melafix. This is on last December.

- Do the fish lose weight or appear bloated? One or two had bloated belly but before those died belly was not bloated. Some had sunken belly.

 

[FishyFishKiller]

I ran some various wood types through Chat GPT.

Eucalyptus releases toxins to fish.
Eucalyptus wood is generally not considered safe for aquariums. It contains high levels of oils and tannins that can be toxic to fish and other aquatic life. Even after extensive drying or curing, eucalyptus can still release harmful substances into the water, affecting water quality and potentially causing health issues for fish and invertebrates.

Safer Alternatives:​

• Driftwood Types: Mopani, Malaysian, Spider Wood, and Manzanita are aquarium-safe after proper curing.
• Cholla Wood: Great for shrimp tanks and provides natural hiding spots.
• Bogwood: Common in aquariums and releases beneficial tannins if soaked properly.

If you specifically want to try eucalyptus, it would require heavy curing, boiling, and soaking for weeks or even months with frequent water changes — but even then, it remains risky. Better to stick with proven aquarium-safe woods!

 

[Andy Sager]

In all honesty, the proper water for livebearers, ( Hard alkaline water) is not the best for shrimp ( soft neutral to acidic water) so if the shrimp are living, the water is probably not the best for livebearers.
The white stringy poop is usually a sign of not eating or internal worms. Some livebearers ( i.e. Guppies) have a bad reputation for having worms. The medication you added will probably treat external parasites but highly unlikely will treat internal ones. I've never used this product so I can't say for sure. How long did you have these fish before they started acting this way? Did you quarantine them before adding them to the main tank? If so, for how long?

 

[ramanan]

In all honesty, the proper water for livebearers, ( Hard alkaline water) is not the best for shrimp ( soft neutral to acidic water) so if the shrimp are living, the water is probably not the best for livebearers.
The white stringy poop is usually a sign of not eating or internal worms. Some livebearers ( i.e. Guppies) have a bad reputation for having worms. The medication you added will probably treat external parasites but highly unlikely will treat internal ones. I've never used this product so I can't say for sure. How long did you have these fish before they started acting this way? Did you quarantine them before adding them to the main tank? If so, for how long?

Thanks for the quick response. I had them for more than 2 months. There were thriving since this issue happened start of this month. There are about 3 batches of fires. form platy and one molly. All that time I had same driftwood same plants but bought a plant during mid February. I live in Sydney Australia, here water is soft and the ph is exactly 7.0 and chlorine is zero. . Anyway I add prime in exact dosage along with seachem stability.

Please see attached photos for the water parameters. Nitrite/Nitrate take 60 secs to show up so see the first photo for that. All others show up in 15secs. Other two photos shows that.

 

[ramanan]

I ran some various wood types through Chat GPT.

Eucalyptus releases toxins to fish.
Eucalyptus wood is generally not considered safe for aquariums. It contains high levels of oils and tannins that can be toxic to fish and other aquatic life. Even after extensive drying or curing, eucalyptus can still release harmful substances into the water, affecting water quality and potentially causing health issues for fish and invertebrates.

Safer Alternatives:​

• Driftwood Types: Mopani, Malaysian, Spider Wood, and Manzanita are aquarium-safe after proper curing.
• Cholla Wood: Great for shrimp tanks and provides natural hiding spots.
• Bogwood: Common in aquariums and releases beneficial tannins if soaked properly.

If you specifically want to try eucalyptus, it would require heavy curing, boiling, and soaking for weeks or even months with frequent water changes — but even then, it remains risky. Better to stick with proven aquarium-safe woods!

Initially I suspected that but the not many don't comment negatively. Isn't API Melafix which contain the similar type of oil which is good for fish? I had this drift wood after extensive treatment. All were thriving until recently (starting 3.5 weeks back). BTW it started after water change. I added Prime little be lower end of the dosage. Changed 40L and added about 0.8ml. Since I changed water couple of time to add Board spectrum remedy. Now I have only 3 baby platies from second and third batch. There were not eating much and have sunken belly but live till now. They are not active. I hope it survives. All others babies and adult are gone. So sad to see them die.
It is so mysterious and no one is able to provide a solution for this.

 

[Andy Sager]

Thanks for the quick response. I had them for more than 2 months. There were thriving since this issue happened start of this month. There are about 3 batches of fires. form platy and one molly. All that time I had same driftwood same plants but bought a plant during mid February. I live in Sydney Australia, here water is soft and the ph is exactly 7.0 and chlorine is zero. . Anyway I add prime in exact dosage along with seachem stability.

Please see attached photos for the water parameters. Nitrite/Nitrate take 60 secs to show up so see the first photo for that. All others show up in 15secs. Other two photos shows that.

As I suspected, your water is not really "livebearer" water. Good "livebearer" water is pH: 7.6-7.8 ( 7.0 is the lowest range the fish can live temporarily, not permanently.) General Hardness: Moderate= 60-120 PPM Hard= 120-180 ppm Very Hard 180+. Livebearers like moderately hard to hard water. And none of these values are good for freshwater shrimps. That means you would have to alter your water to keep livebearers in the best of health. To be honest tho, you are better off not changing your water's parameters but change the fish you select to ones that like your water's parameters out of the tap.

Regarding using PRIME and stability, you only need to use the stability when you are starting a tank but once your tank is cycled, the nitrifying microbes are not in the water column so no need to add it when doing water changes. PRIME should be used to remove or detoxify anything in your water that is not fish safe. You can add the Stability when you add fish or other living organisms to help your microbe colony catch up to the rise in ammonia production faster.

So I'd say your fish losses were coming from a lack of minerals causing organ failure and cellular disfunction.

Just an FYI, when the problem is the water ( i.e. pollution, high nitrates, etc.) all the fish/livestock suffer. When it's only one type or one family of the livestock, it's usually improper parameters or improper diet. In your case, it's improper parameters.

Hope this helps.

 

[ramanan]

As I suspected, your water is not really "livebearer" water. Good "livebearer" water is pH: 7.6-7.8 ( 7.0 is the lowest range the fish can live temporarily, not permanently.) General Hardness: Moderate= 60-120 PPM Hard= 120-180 ppm Very Hard 180+. Livebearers like moderately hard to hard water. And none of these values are good for freshwater shrimps. That means you would have to alter your water to keep livebearers in the best of health. To be honest tho, you are better off not changing your water's parameters but change the fish you select to ones that like your water's parameters out of the tap.

Regarding using PRIME and stability, you only need to use the stability when you are starting a tank but once your tank is cycled, the nitrifying microbes are not in the water column so no need to add it when doing water changes. PRIME should be used to remove or detoxify anything in your water that is not fish safe. You can add the Stability when you add fish or other living organisms to help your microbe colony catch up to the rise in ammonia production faster.

So I'd say your fish losses were coming from a lack of minerals causing organ failure and cellular disfunction.

Just an FYI, when the problem is the water ( i.e. pollution, high nitrates, etc.) all the fish/livestock suffer. When it's only one type or one family of the livestock, it's usually improper parameters or improper diet. In your case, it's improper parameters.

Hope this helps.

Thanks you for for time and advice. Appreciate it
Got few more questions.
" To be honest tho, you are better off not changing your water's parameters but change the fish you select to ones that like your water's parameters out of the tap. " - you mean livebearer raised in the lower PH level or different type of fish?
Any thoughts why it survived but was thriving for 2 months? 4 females having more than 20 fries
I am bit generous on Seachem stability. So should I not use it on this established tank ? (now I have doubts whether it is established even though nitrites are in safe level) Stop all together and use only PRIME. I also use 1 teaspoon of plain crystal salt per 10 liters. Any advice is valuable for me. I am a novice in aquarium keeping.

"When it's only one type or one family of the livestock, it's usually improper parameters or improper diet. In your case, it's improper parameters." This is very good conclusion. little bit of clarity I am getting. Could it be any protozoan or parasites ? If that is the case shrimps and snails will survive? To me it is like mystery not sure how can I solve it.

Now I have only 3 babies from the fries. Still surviving. Still I haven't bought any new fish. Any advice on how to get this started again?

 

[Andy Sager]

Thanks you for for time and advice. Appreciate it
Got few more questions.
" To be honest tho, you are better off not changing your water's parameters but change the fish you select to ones that like your water's parameters out of the tap. " - you mean livebearer raised in the lower PH level or different type of fish?
Any thoughts why it survived but was thriving for 2 months? 4 females having more than 20 fries

Because it's a process where the fish doesn't get the minerals it needs to stay healthy. This goes down to the cellular level. Think of it as a sealed box of oxygen and water and a single fish in it. The fish will live at the start because there is plenty of oxygen but as time goes by and there is less oxygen, it won't do as well and as the oxygen level reduces, the worse the fish will will do until finally, it can't live. If it were a situation where there was say, a poison in the box, the fish would have died instantly.

I am bit generous on Seachem stability. So should I not use it on this established tank ? (now I have doubts whether it is established even though nitrites are in safe level) Stop all together and use only PRIME. I also use 1 teaspoon of plain crystal salt per 10 liters. Any advice is valuable for me. I am a novice in aquarium keeping.

Your tank is fully established when your ammonia and nitrite levels have gone up and then come down to zero and your nitrate level is increasing. You can see that in this graph of the cycling process.

"When it's only one type or one family of the livestock, it's usually improper parameters or improper diet. In your case, it's improper parameters." This is very good conclusion. little bit of clarity I am getting. Could it be any protozoan or parasites ?

Always a possibility but a highly unlikely probability.

If that is the case shrimps and snails will survive?

Actually, shrimps and snails are known carriers of parasites as they are used as intermediate hosts by parasites that need a higher lifeform to conclude their life cycle.

To me it is like mystery not sure how can I solve it.

If only fish could tell us what the issue is, there would be more successful aquarists. Sometimes it's just a guess and other times, it's a similar situation seen before and after unsuccessful treatments were performed, successful ones are documented and reused. This is why I had a mountain of books on fish and fish keeping when I got started so I didn't do too many unsuccessful things.

Now I have only 3 babies from the fries. Still surviving. Still I haven't bought any new fish. Any advice on how to get this started again?

I do not have high hopes for them to have a long life but fish can be adaptable so you never know. If you see them start to act weird or look like the others as they died, your choice is to place them in the correct water parameters ( in a separate tank I suggest) or euthanize them since there is no disease involved to treat.

Hope this helps.