Hi, five days ago I added two molly fish and a mystery snail to my fully cycled 10 gallon tank (fishless cycled). I checked the ammonia and nitrites twice a day using API master kit and they were both at zero ppm. One of the fish died after two and a half days. I did a 20% water change after the first fish died and the second fish died on the fifth day. The snail is still happily snailing around the tank. The water still reads 0 ammonia 0 nitrite and very low levels of nitrate. oh also my tank heater is set on 77 degrees and I also added API Stress Coat to the tank. I don’t know what I did wrong to kill them and would appreciate any help!
Molly Fish Dying :(
- Thread starter Mwight
- Start date
How do you condition new tank water added to the tank? What is your tap water parameters?
If everything’s perfect and they still died, you may have bought them sick
Oh the stress coat was the water conditioner I used so maybe that was part of the problem then. I also had my tap and tank water both tested at petsmart and they said neither had any chlorine and the other parameters looked good at well.. but I just retested it and my pH is pretty close to 8 even. And the general water hardness is a little over 120 ppm and the carbonate hardness also read a little over 120 ppm using test strips.
I did think about that, but they both seemed really active and happy up until the days each died on which makes me think it’s something I did?
There are some issues that will be contributing factors though not necessarily directly responsible for the fairly rapid deaths.
First involves water parameters, which are GH, KH (Alkalinity), pH and temperature. The GH is certainly a problem for mollies, they must have harder water. GH here is 120 ppm (= 6 dH) but it should be no less than 240 ppm (= 12 dH) or higher. Since the mollies have died, do not get any more once this issue is resolved because they will not be in good shape in water this soft.
Re the API Stress Coat, here again not likely to kill them unless it was overdosed, but aloe vera is likely trouble for fish gills and it also affects the Oxygen balance, so change to another conditioner going forward. If all your tap water has is chlorine or chloramine, the best to use is API's Tap Water Conditioner. If there is ammonia, nitrite or nitrate in the tap water (on its own), another conditioner might be advisable, but this one is basic and very effective, and you use very little. Never over-dose conditioners, they are not as "safe" as some think.
Third point, when you get stores to do water tests, always insist they give you the number. What they consider "good" may be far from it.
Fourth, many fish, especially mass-produced fish like common livebearers are anything but healthy. There can be genetic issues, internal pathogens, or injury from netting and bagging the fish.
A 10g ios too small a tank for mollies even if the water was suited. Have a look at soft water fish, like the tetras and rasboras. Some will be OK in this sized tank, but ask on the forum before acquiring. These fish are shoaling and they must have a group of several of them.
First involves water parameters, which are GH, KH (Alkalinity), pH and temperature. The GH is certainly a problem for mollies, they must have harder water. GH here is 120 ppm (= 6 dH) but it should be no less than 240 ppm (= 12 dH) or higher. Since the mollies have died, do not get any more once this issue is resolved because they will not be in good shape in water this soft.
Re the API Stress Coat, here again not likely to kill them unless it was overdosed, but aloe vera is likely trouble for fish gills and it also affects the Oxygen balance, so change to another conditioner going forward. If all your tap water has is chlorine or chloramine, the best to use is API's Tap Water Conditioner. If there is ammonia, nitrite or nitrate in the tap water (on its own), another conditioner might be advisable, but this one is basic and very effective, and you use very little. Never over-dose conditioners, they are not as "safe" as some think.
Third point, when you get stores to do water tests, always insist they give you the number. What they consider "good" may be far from it.
Fourth, many fish, especially mass-produced fish like common livebearers are anything but healthy. There can be genetic issues, internal pathogens, or injury from netting and bagging the fish.
A 10g ios too small a tank for mollies even if the water was suited. Have a look at soft water fish, like the tetras and rasboras. Some will be OK in this sized tank, but ask on the forum before acquiring. These fish are shoaling and they must have a group of several of them.
Thank you that is incredibly helpful! That has given me a few more questions though. First Is the water too soft for my mystery snail and if so is there a way you would recommend to harden it? Second how many tetras would you recommend for a 10 gallon tank and how many would be safe to add at a time to avoid spiking the ammonia and such but also not stress them from not having enough tank mates? And third, for in the future what is the minimum tank size you would recommend for Molly fish?
Members with experience with mystery snails can better answer the first part, but 6 dH may be sufficient. As for hardening it, this is not a safe or easy road. I've no idea of your experience with tropical fish, but it is always easier to select fish suited to your water parameters. It means no fuss with water changes, or emergencies. Preparing water in containers and then using it for water changes can work, but it adds another level of complexity. The other thing is that there are many more soft water species than hard water when it comes to small tanks.
Tetras and other shoaling fish tend to be in better shape (= healthier, less stressed) with numbers in the 10-12 range minimum, and up. In a 10g this means mostly "nano" fish, like Ember Tetras, pygmy cories (if you have sand), dwarf rasboras, etc. There are some lightly larger fish that would work too. But you want to keep in mind that the more there are in the species group, the better. For example, for a few years I had a 10g with 12 Boraras brigittae (a dwarf rasbora species) and 11 pygmy cories. Had I wanted to, I could easily have found a third upper fish to add in similar numbers.
Mollies are not small fish--if they live and are healthy. Males can reach 3 inches, females five and even six inches. This means a tank that is in the 30-inch length but much preferably 36 inches. They are not particularly active but they do produce a lot of waste so I would look at a 40 gallon 3-foot tank as minimum if this were my intention.
I will also just mention that mollies are particularly sensitive to ammonia and nitrite, and high nitrate. You earlier mentioned that ammonia and nitrite were at zero, so if the tests were accurate, that may not have been the issue.
Agreed! My largest, longest lived black mollies lived for more than 6-7 years, and grew very large, using the entirety of the 57g tank they lived in.
This is the only part of your comment that I disagree with - my experience with mollies is that they're very active. Short-finned and intensely curious (and quite frankly, greedy) I find them to be strong swimmers who will use all the space they have, and investigate every corner and new item/interference during tank maintenance in hope of food. Mine also became quite hand tame, coming to eat from my hands without any sign of fear.
In my mind I compare fish that are active to danios. The mollies I had many years ago now did not swim frantically around like that, lol, so a "race track" is not necessary but a 40g 3-foot tank should work.
Ah well, that explains it! LOL. Danios are little speed demons, haha!
Okay thank you so much for your help!
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