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Mollies/Platys dying one by one

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LindaAnn6

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Hello,

So I have a 130 litre tropical aquarium that has been running for at least 7 years now. For the past year I’ve only had black skirt tetras, black phantom tetras and rasboras, all of which are doing fine. About 6 weeks ago I purchased 4 Platys and 4 mollies and didn’t even think to quarantine them. Slowly one by one the Platys and mollies have been dying. One day it will be swimming around and eating normally, then over the next 3 days or so it will start spending more and more time lying on the bottom of the tank (though still coming up to eat, then slowly sinking back to the bottom) before dying, whilst the others swim and eat fine. To me they look fine physically so I’m stumped as to what is causing this.

I had my 4th death yesterday and it looks as though the 5th will die by tomorrow (it’s still swimming up to eat as of 10 minutes ago). I’ve just noticed that the one that is currently sickest seems to have a round mark/hole on it that wasn’t there yesterday..

After the first death I started dosing weekly with Aqua One Broad Spectrum Remedy for 4 weeks (which obviously hadn’t helped). The past 2 days I’ve been dosing with API Pimafix instead, however now the remaining mollies/platys are also starting to spend more time hiding/at the bottom of the tank. I’m at a total loss. Please help!

Tested water yesterday:
Ph 7.6
Ammonia 0
Nitrite 0
Nitrate 40-80(max)
 

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Hello,

So I have a 130 litre tropical aquarium that has been running for at least 7 years now. For the past year I’ve only had black skirt tetras, black phantom tetras and rasboras, all of which are doing fine. About 6 weeks ago I purchased 4 Platys and 4 mollies and didn’t even think to quarantine them. Slowly one by one the Platys and mollies have been dying. One day it will be swimming around and eating normally, then over the next 3 days or so it will start spending more and more time lying on the bottom of the tank (though still coming up to eat, then slowly sinking back to the bottom) before dying, whilst the others swim and eat fine. To me they look fine physically so I’m stumped as to what is causing this.

I had my 4th death yesterday and it looks as though the 5th will die by tomorrow (it’s still swimming up to eat as of 10 minutes ago). I’ve just noticed that the one that is currently sickest seems to have a round mark/hole on it that wasn’t there yesterday..

After the first death I started dosing weekly with Aqua One Broad Spectrum Remedy for 4 weeks (which obviously hadn’t helped). The past 2 days I’ve been dosing with API Pimafix instead, however now the remaining mollies/platys are also starting to spend more time hiding/at the bottom of the tank. I’m at a total loss. Please help!

Tested water yesterday:
Ph 7.6
Ammonia 0
Nitrite 0
Nitrate 40-80(max)
Hey there I would say that tank is like 30-35 gallons correct? Mollies and platys need space and an estimate is to every inch 1 gallon, but this is the the bare minimum. Im not sure what the other fishes you have require but maybe from over loading the tank with many new fish at once. Always be checking the water parameters to see if there is anything in the water that could be causing fish to get sick! Because if its only the platys and mollys dying I would think it had to do something with the size of the tank and the way the were introduced into the tank
 
Hi and welcome to the forum :)

Can you post pictures of all the new fish?

What is the GH (general hardness) and KH (carbonate hardness) of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).

Platies need a GH around 200ppm and a pH above 7.0.
Mollies need a GH above 250ppm and a pH above 7.0. Your pH is fine for them but the GH might be too low.

Tetras and rasboras come from soft water.

---------------------
Your nitrates are high and you want to try and keep them as close to 0ppm as possible, and always aim to keep them below 20ppm.

Doing bigger water changes or more frequent water changes will help get nitrates down. floating plants like Water Sprite will also help reduce them.

---------------------
DO THE FOLLOWING.
Wipe the inside of the glass down with a clean fish sponge. This removes the biofilm on the glass and the biofilm will contain lots of harmful bacteria, fungus, protozoans and various other microscopic life forms.

Do a 75% water change and gravel clean the substrate each day until the nitrates are below 20ppm. The water changes and gravel cleaning will reduce the number of disease organisms in the water and provide a cleaner environment for the fish to recover in.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

Clean the filter if it hasn't been done in the last 2 weeks. However, if the filter is less than 6 weeks old, do not clean it. Wash the filter materials/ media in a bucket of tank water and re-use them. Tip the bucket of dirty water on the garden/ lawn. Cleaning the filter means less gunk and cleaner water with fewer pathogens.

Increase surface turbulence/ aeration when using salt or medications because they reduce the dissolved oxygen in the water.

Add some salt, (see directions below).

---------------------
SALT
You can add rock salt (often sold as aquarium salt) or swimming pool salt to the aquarium at the dose rate of 1 heaped tablespoon per 20 litres of water. If there is no improvement after 48 hours you can double that dose rate so there is 2 heaped tablespoons of salt per 20 litres.

Keep the salt level like this for at least 2 weeks but no longer than 4 weeks otherwise kidney damage can occur. Kidney damage is more likely to occur in fish from soft water (tetras, Corydoras, angelfish, Bettas & gouramis, loaches) that are exposed to high levels of salt for an extended period of time, and is not an issue with livebearers, rainbowfish or other salt tolerant species.

The salt will not affect the beneficial filter bacteria, fish, plants, shrimp or snails.

After you use salt and the fish have recovered, you do a 10% water change each day for a week using only fresh water that has been dechlorinated. Then do a 20% water change each day for a week. Then you can do bigger water changes after that. This dilutes the salt out of the tank slowly so it doesn't harm the fish.

If you do water changes while using salt, you need to treat the new water with salt before adding it to the tank. This will keep the salt level stable in the tank and minimise stress on the fish.
 
Hey there I would say that tank is like 30-35 gallons correct? Mollies and platys need space and an estimate is to every inch 1 gallon, but this is the the bare minimum. Im not sure what the other fishes you have require but maybe from over loading the tank with many new fish at once. Always be checking the water parameters to see if there is anything in the water that could be causing fish to get sick! Because if its only the platys and mollys dying I would think it had to do something with the size of the tank and the way the were introduced into the tank
Thanks for your reply. I’ve just recalculated and the tank is 36 gallons. All up there are currently 13 fish in the tank. The largest being a 5cm platy (which is now constantly hiding up by the top of the heater). When introduced to the tank they were acclimated by floating the bag in the tank and adding a little tank water to the bag every 10 minutes for 30 minutes.
 
Hi and welcome to the forum :)

Can you post pictures of all the new fish?

What is the GH (general hardness) and KH (carbonate hardness) of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).

Platies need a GH around 200ppm and a pH above 7.0.
Mollies need a GH above 250ppm and a pH above 7.0. Your pH is fine for them but the GH might be too low.

Tetras and rasboras come from soft water.

---------------------
Your nitrates are high and you want to try and keep them as close to 0ppm as possible, and always aim to keep them below 20ppm.

Doing bigger water changes or more frequent water changes will help get nitrates down. floating plants like Water Sprite will also help reduce them.

---------------------
DO THE FOLLOWING.
Wipe the inside of the glass down with a clean fish sponge. This removes the biofilm on the glass and the biofilm will contain lots of harmful bacteria, fungus, protozoans and various other microscopic life forms.

Do a 75% water change and gravel clean the substrate each day until the nitrates are below 20ppm. The water changes and gravel cleaning will reduce the number of disease organisms in the water and provide a cleaner environment for the fish to recover in.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

Clean the filter if it hasn't been done in the last 2 weeks. However, if the filter is less than 6 weeks old, do not clean it. Wash the filter materials/ media in a bucket of tank water and re-use them. Tip the bucket of dirty water on the garden/ lawn. Cleaning the filter means less gunk and cleaner water with fewer pathogens.

Increase surface turbulence/ aeration when using salt or medications because they reduce the dissolved oxygen in the water.

Add some salt, (see directions below).

---------------------
SALT
You can add rock salt (often sold as aquarium salt) or swimming pool salt to the aquarium at the dose rate of 1 heaped tablespoon per 20 litres of water. If there is no improvement after 48 hours you can double that dose rate so there is 2 heaped tablespoons of salt per 20 litres.

Keep the salt level like this for at least 2 weeks but no longer than 4 weeks otherwise kidney damage can occur. Kidney damage is more likely to occur in fish from soft water (tetras, Corydoras, angelfish, Bettas & gouramis, loaches) that are exposed to high levels of salt for an extended period of time, and is not an issue with livebearers, rainbowfish or other salt tolerant species.

The salt will not affect the beneficial filter bacteria, fish, plants, shrimp or snails.

After you use salt and the fish have recovered, you do a 10% water change each day for a week using only fresh water that has been dechlorinated. Then do a 20% water change each day for a week. Then you can do bigger water changes after that. This dilutes the salt out of the tank slowly so it doesn't harm the fish.

If you do water changes while using salt, you need to treat the new water with salt before adding it to the tank. This will keep the salt level stable in the tank and minimise stress on the fish.
Thanks so much. I have no idea what the water hardness is like so I will have it tested today. Will also do a 75 percent water change too. Last water change and filter clean I did was 2 days ago (25 percent). I have also attached photos of two of the other new fish. Will have to get a photo of the other one later as it’s currently hiding in a large decoration.
 

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The fish are skinny and the orange one has clamped fins. They probably have gill flukes, intestinal worms and external protozoan parasites.

The salt will deal with any gill flukes and external protozoa. In a few weeks time, assuming they have recovered a bit, you can try deworming them. See section 3 of the following link for information on deworming fish.

In the mean time, increase feeding to 3-5 times a day to try and fatten them up. If they have intestinal worms or gill flukes, the fish will be suffering from anemia (low blood levels) due to the parasites sucking the blood out of them. The extra food will help the fish produce more blood and hopefully keep them alive until they can be treated for worms.

Do big daily water changes and gravel cleans when feeding more often to keep the water in good shape.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.
 
The fish are skinny and the orange one has clamped fins. They probably have gill flukes, intestinal worms and external protozoan parasites.

The salt will deal with any gill flukes and external protozoa. In a few weeks time, assuming they have recovered a bit, you can try deworming them. See section 3 of the following link for information on deworming fish.

In the mean time, increase feeding to 3-5 times a day to try and fatten them up. If they have intestinal worms or gill flukes, the fish will be suffering from anemia (low blood levels) due to the parasites sucking the blood out of them. The extra food will help the fish produce more blood and hopefully keep them alive until they can be treated for worms.

Do big daily water changes and gravel cleans when feeding more often to keep the water in good shape.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.
Thanks for that, I did suspect parasites. I’ve tested the water hardness before a water change with an API kit. KH took 4 drops which would be 71.6ppm and GH took 18 drops which it says is between 200-400ppm. Am about to do a large water change with prime added as my water conditioner.
 
1 drop = 17.9ppm (or mg/ L).
18 drops = 320ppm. That is pretty hard water and ideal for mollies and African Rift Lake cichlids. It's too high for most tetras, rasboras and Corydoras long term health.
 

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