Molly on bottom, not pregnant

I have a dalmation molly that has been in my 20 gal tank for months and lately has been resting at the bottom of the tank or on a surface and looks a little pale.

No labored breathing or anything but the dorsal fin is clamped and the ammonia, nitrite, and nitrate are all 0 or within range. All my other fish are acting normal.

Hi and welcome to the forum

I need a better picture of the fish to confirm this, but it appears the fish has dropsy. This is characterised by the scales sticking out sideways. Dropsy is usually caused by an internal bacterial infection and there is no cure for it. If the fish's scales are sticking out sideways from the body, you should euthanise it.

If the scales are not sticking out from the body, you can try adding salt. Before you add salt, do a 75% water change and gravel clean the substrate. Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

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You can add rock salt (often sold as aquarium salt), sea 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.

If you only have livebearers (guppies, platies, swordtails, mollies), goldfish or rainbowfish in the tank you can double that dose rate, so you would add 2 heaped tablespoons per 20 litres and if there is no improvement after 48 hours, then increase it so there is a total of 4 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, 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 but the higher dose rate will affect some plants. The lower dose rate will not affect plants.

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.

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What is the GH (general hardness) and pH 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).

Mollies need water with a GH around 250ppm and a pH above 7.0. If the GH is too low, the fish will have problems.

Thank you so much for your quick reply! I do have a copy of my drinking water report from the city which I received a month or so ago with information such as heavy metals, nitrates, etc. I'm not sure how to find general hardness though since that isnt really mentioned.

I checked for upturned scales and I don't see any. I just did a 30% water changed and a light vacuum to see if that would help and he seems a little more lively now. I'm not exactly sure what the issue was since ammonia and nitrite were 0 and nitrate was less than 40 ppm. pH is kept in the 7.5-7.6 range as well. I use water conditioner to remove the chlorine too.

I appreciate your help and fingers-crossed that he stays healthy!

Edit: I have a pleco in the tank too so I'm not sure how salt resistant he is, if at all.

Nitrate really should be below 20ppm. As for the pleco, he shoukd be able to withstand about half a dose. Someone correct me if I'm wrong though.

Colin_T said:

You can add rock salt (often sold as aquarium salt), sea 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.

Click to expand...

This dose rate is suitable for all freshwater fishes that don't naturally occur in hard or brackish water, including plecos, tetras, barbs, gouramis, angelfish, etc.

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Do bigger water changes. All suckermouth catfish (including plecos) produce huge amounts of waste and this encourages bacteria and protozoa to grow in the tank. I recommend doing a 75% water change and gravel cleaning the entire substrate (except under live plants) every week under normal circumstances, and every day if there is a problem with the fish. The big water changes dilute nutrients and disease organisms in the water and buy some time for us to work out what is going on.

You do water changes for 2 main reasons.
1) to reduce nutrients like ammonia, nitrite & nitrate.
2) to dilute disease organisms in the water.

Fish live in a soup of microscopic organisms including bacteria, fungus, viruses, protozoans, worms, flukes and various other things that make your skin crawl. Doing a big water change and gravel cleaning the substrate on a regular basis will dilute these organisms and reduce their numbers in the water, thus making it a safer and healthier environment for the fish.

If you do a 25% water change each week you leave behind 75% of the bad stuff in the water.
If you do a 50% water change each week you leave behind 50% of the bad stuff in the water.
If you do a 75% water change each week you leave behind 25% of the bad stuff in the water.

Imagine living in your house with no windows, doors, toilet, bathroom or anything. You eat and poop in the environment and have no clean air. Eventually you end up living in your own filth, which would probably be made worse by you throwing up due to the smell. You would get sick very quickly and probably die unless someone came to clean up regularly and open the place up to let in fresh air.

Fish live in their own waste. Their tank and filter is full of fish poop. The water they breath is filtered through fish poop. Cleaning filters, gravel and doing big regular water changes, removes a lot of this poop and makes the environment cleaner and healthier for the fish.

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As mentioned by FishFinatic77, you want the nitrates as low as possible and 0ppm is great. However, that is quite difficult to do in most tanks so we suggest trying to keep nitrates below 20ppm.