Molly Behavior and Feeding Issue

For context, I have a 30 gal tank with Current Satellite LEDs, moderately planted with gravel bottom, mostly hornwart, water sprite, swords and java ferns, lots of driftwood, with 15 cardinals, 8 pygmy corys and 5 cherry shrimp. I have two female lyretail mollies and one black sailfin male molly. Water is 78 degrees, hang on back filter so should be well oxygenated. Water parameters are 7.3 pH, ammonia 0, nitrites 0, nitrates 5, GH 50~75, KH 140. I am using softened wellwater. I treat the water with aquavitro seed and dechlorinator/balancer.

All mollies will occasionally come to the surface and do what looks like a gulping motion for a few seconds, then descend. My (possibly pregnant) lyretail female does this most often, upwards of several times a minute. She will also make gulping motions when underwater; the others don't. The females also exhibit glass surfing/pacing behavior, often near the bottom or in corners. I would appreciate help diagnosing the issue.

Now to food: I feed my cardinals and mollies about two pinches of hikari floating tetra pellets (which they consume in roughly 40 to 50 seconds) twice daily. I feed my corys 2 hikari sinking wafers, which usually takes 30+ minutes to eat, given the cardinals don't find it. I feed my shrimp about 10 hikari shrimp pellets once daily, and have the same issue with cardinals taking their food. I have had difficulty getting my mollies to eat; often they either arrive too late to feedings or eating halfhearted amounts. My local store assured me they are fine eating the tetra pellets, but for the time being I am feeding them the shrimp pellets as they are too big for my cardinals to eat. I would feel a lot better if I knew they were getting enough to eat for sure.

The mollies are probably reacting to the soft water. They need over 250 ppm and yours is much lower than that. Your other fish are soft water fish.

Gemtrox42 said:

I am using softened wellwater

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What type of water softener? There ate a few types but those which replace the hardness minerals with sodium (or sometimes potassium) should not be used for fish tanks. Fresh water fish haven't evolved to cope with sodium (or potassium) in the water.

I have been keeping mollies on and off for about 3 years now, and have had the same water used for the whole time, and neither of the local fish hobbyists I go to have said the water was too soft for mollies. Can you elaborate on the effects of soft water on mollies? Would it not visibly harm them in some cases? Also, how would I balance their needs with my softwater fish?

My water softener uses sodium chloride, not pure sodium. Is that still a problem?

Gemtrox42 said:

I have been keeping mollies on and off for about 3 years now, and have had the same water used for the whole time, and neither of the local fish hobbyists I go to have said the water was too soft for mollies. Can you elaborate on the effects of soft water on mollies? Would it not visibly harm them in some cases? Also, how would I balance their needs with my softwater fish?

My water softener uses sodium chloride, not pure sodium. Is that still a problem?

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Several things can happen when hard water fish are put in soft water.
- Organs and brain shutdown/failure due to lack of necessary minerals
- Skin burning from the acidity of the water.
- Loss of muscle control, due to high stress
Your mollies are showing symptoms of organ failure due to acidic water that they can not cope with.
There are more issues but these are the ones I could think of off the top.

Any chance of some pictures and short 60 second video of the fish doing the unusual behaviour?
If the pictures are too big for the website, set the camera's resolution to its lowest setting and take some more. The lower resolution will make the images smaller and they should fit on this website. Check the pictures on your pc and find a couple that are clear and show the problem, and post them here. Make sure you turn the camera's resolution back up after you have taken the pics otherwise all your pictures will be small.

If the video is too big for this website, post it on YouTube and copy & paste the link here. We can view it at YouTube. If you are using a mobile phone to take the video, have 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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Sodium chloride is bad for cardinal tetras and Corydoras. It can damage their kidneys in the long term.

A pH of 7.3 is fine for the mollies but they would do better in harder water. They naturally occur in water with lots of minerals and can have issues in soft water. Most of the problems they develop in soft water cannot be seen from the outside and are only visible if you cut the fish open and look at its organs under a microscope. Something we don't encourage doing until the fish dies of natural causes.

Realistically, it would be better for your fish if you had a soft water tank for the tetras and a hard water tank for the livebearers.

You should look into rain water, distilled water, reverse osmosis water, or a water softener that does not contain/ use sodium or sodium chloride. This would give the tetras soft water that is free of salt, and they would be happier.

Ok, so let me make sure I have this right - my mollies problems are signs of and/or most likely related to water salinity issues, with hardness being the secondary problem. Also, while it may not be visible, all my fish will be living shorter and worse lives due to salty water.

I will monitor my fish for a week, and also find a water salinity test before doing anything drastic. If I post the results here, can you tell me if the salt levels are too high? And is there no situation in which tetras and mollies could be kept in the same tank? I'd rather not rehome and redo my tank if I can help it.

I need pictures and video of the mollies before I can even guess what the problem is. It could be boredom, natural behaviour or associated with water quality/ chemistry.

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The amount of salt from an ion exchange unit will be minimal and you probably won't be able to test it without a refractometer, and these are expensive.

Any salt is bad for soft water fishes like neon and cardinal tetras that come from the Amazon. These soft water fishes never evolved to live with salt in the water and being exposed to sodium chloride for long periods of time will shorten their lives.

The salt is not bad for the mollies and they can be found in waterways containing salt (sodium chloride) as well as waterways that don't contain salt.

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There is no real happy medium for these two groups of fish. Soft water fish like tetras come from soft water with a very low mineral content.

Mollies come from hard water. If you have hard water the mollies do well but the tetras suffer. If you have soft water the tetras do well but the mollies suffer.

If you have the water somewhere in between, they all suffer.

You can keep the mollies in the tank but they probably won't live as long as if they were kept in hard water.

This keeps getting better and better. I woke up and now 4 of my cardinals are suffering from ich. And the treatments say to use salt, well I should already have salt in the water from the softener. So what gives? And do you know if Ich-X is the next best way to treat the tank?

Side note I know its not your problem but I am seriously going crazy with the amount of contrary info I'm getting.

Are you sure they have white spot?
Can you post some pictures so we can confirm white spot?
Have you added anything to the tank in the last 2 weeks?

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Salt does nothing to the white spot parasite.

Ich-X contains Malachite Green, which will kill white spot and velvet parasites, as well as any other external protozoan parasites.

*NB* Malachite Green is a carcinogen (causes cancer) so handle with care and do not inhale, ingest or get any on your body.

However, the safest treatment for white spot is to raise the water temperature to 30C (86F) and keep it there for 2 weeks. The parasites can't tolerate the high temperature and die. You don't need chemicals and most tropical fish tolerate the heat quite well for a couple of weeks.

Before you raise the water temperature, do a 75-80% water change and complete gravel clean. Make sure any new water is free of chlorine/ chloramine before it's added to the tank. Clean the filter too. This removes a lot of the parasites from the tank so there are fewer to infect the fish. Then increase the aeration/ surface turbulence to maximise the oxygen levels in the water, and raise the temperature.

Sorry for the resolution, these are the best I could get. Luckily I got it early so hopefully it can be minimized. Interesting that you say salt does nothing, most websites recommend aquarium salts as the first thing. Getting Ich-x and an adjustable heater as I didn't have them before. Will change water as well.

Is cleaning the whole filter really necessary, Id like to keep my biofilter. And I don't have aeration on hand, should my hang on back filter be enough oxygen? Also can you elaborate on what you mean by complete gravel clean?

I can't tell anything from those pictures.

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White spot lives in fresh, brackish and salt water. Salt does nothing to it.

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If you use heat treatment (30C for 2 weeks), you don't need to use the chemicals (Ich-X). You either use heat or chemicals but not both.

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If there is white spot in the tank, there will be parasites in the filter too. Having a clean tank & filter will mean any medication (if you choose to use chemicals) will go to treating the fish and not be wasted on bacteria and other disease organisms in the substrate or filter media/ materials.

When you clean the filter, you only wash the filter media in a bucket of tank water and re-use it. The bucket of dirty tank water gets poured on the lawn.

You don't throw filter media away and replace it unless it is falling apart. The only exception to this is carbon or Ammogon/ Zeolite. These 2 items should not be used in filters unless there is a problem with the water quality. Even then, they are only temporary measures.

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If you are using heat treatment, a hang on back (HOB) style filter is insufficient to keep oxygen levels at maximum. You normally use an air pump with a piece of airline and an airstone on the end. The pump sits outside the tank (preferable on a shelf higher than the tank) while the airstone sits in the aquarium.

Plastic multicoloured airstones are usually better than sand airstones becaue the plastic ones have bigger holes and don't put as much pressure on the air pump. However, if you can't get plastic multicoloured airstones, then get whatever is available.

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A complete gravel clean simply means using a gravel cleaner (like the one in the following link) to clean the gunk out of the gravel in the aquarium. The gravel stays in the tank and you use the gravel cleaner to suck the gunk out along with some of the tank water.

If you don't have a gravel cleaner, you can buy them from pet shops, online or make your own from a 1, 1.5 or 2 litre plastic drink bottle and a length of garden hose or clear plastic hose.

Check YouTube for how to use a gravel cleaner or ask the pet shop staff to demonstrate how to use one. You don't need a super duper fancy gravel cleaner, just a basic model like the one in the link I posted above.

Ok, I am going with the chemical treatment as I don't have an airstone. One last question - do you just have to submerge the whole filter in water to clean it? Or are there more things you should do? Also I am pretty sure, but just wanted to check: when you said clean it in aquarium water, you meant aquarium SAFE water, not the infected water FROM my aquarium, right?

The way to clean a filter is this:

1) turn it off
2) take water out of your tank into a 5 gallon bucket or similar (usually, people clean their filter when doing a water change)
3) take the media out of your filter (sponges, bio balls, cartridges) and place into the 5 gallon bucket.
4) swish each media item around in the tank water. The more you swish, the more you risk wearing off the BB biofilm, so find a happy medium between "dirty" and "too clean". Sponges can and should be squeezed out to get rid of gunk and rotting stuff.
5) replace your filter media in the same order that it was in the filter before
6) prime your filter as necessary
7) turn filter back on and ensure it works.


I left out any mentions of cleaning the filter housing itself, often you do not need to wipe down the internal surfaces unless there is a problem. Depending on the type of filter, it is however a good idea to clean the impeller or pump section to keep it running smoothly.

Did this help?

VERY helpful, thanks. I don't know why I heard clean the filter and thought clean the whole thing! But I won't be putting the media back in this instance because I'm using chemicals. Will update when I'm good. Thanks to everyone who helped, I know this got wildly off topic, but I really appreciate it.

What do you mean you're not putting the media back? Take carbon/zeolite out of the filter but you must put the other stuff back otherwise you risk crashing your cycle -> nitrite/ammonia spikes.

If your tank is older than 6 months this is not as high if a risk, but until you have BB in your substrate and decorations it primarily lives in your filter and not putting the media back means you are taking out the good bacteria.

If you have carbon cartridges , you can cut the filter on the backside and pour out as much of the carbon as you can, and then put the cartridge back. If you have a carbon-impregnated sponge then there may not be as many options, but in all likelihood the carbon is already spent so it may be ok to just leave it in there for now if it cannot be removed, but I would seek additional advice on how to handle a carbon sponge.