Why are my mollies dying?

Factual Questions
1

10 gallon freshwater tank containing plants (amazon sword, java fern), rocks, and increasingly fewer mollies. The two most recent victims were young’uns, born in August, the two survivors of about 20 baby mollies, and my son was very proud that these two had grown up. One of them was half the size of the other. The smaller one succumbed a week ago, the larger one succumbed today. In both cases the day after a partial (2-1/2 gal.) water change (and yes, I did add the dechlorinator). The only molly left is Big Gold, who has been around for awhile. The mollie mama died shortly after producing those 20 babies. (Those two had been in the tank since April.)

Big Gold is now lonely and I don’t know what to do. I’m thinking maybe I should just stick to plants. They are doing very well.

2

Do you have an airstone in the tank? How about adding some Sea Salt to the water? Try those and see what happens.

3

You don’t mention any symptoms. Imagine you’re a doctor, asked to diagnose a patient over the phone. You gotta give with some details.

First line of inquiry, for mollies, though: they like salt in the water, but the plants you mention do NOT. You might have to choose. They also like a lot of vegetable matter in their food. There are algae-based flakes on the market. Or TINY drops of roughly pureed/finely chopped FRESH spinach, WELL washed.

4

Forgot to mention this. Yes, two airstones, undergravel filter.

I also have a powerfilter that I’m not using. I didn’t put it in this tank because then the lid wouldn’t fit on top and I need a secure lid. (Have cat who believes contents of fish tank constitutes cat sushi bar.) Also have added about 1tsp sea salt per two gallons, as I change the water.

5

Fish die often even under good conditions. I like to have Mollies because of their colors and size, the big bonus is they are live bearing fish. I found they did better in what you would consider yucky water, but they lived long and prospered. Try a biological filter, the fish do much better. Mollies like a little salt added to the water, and a small amount actualy helps recovery of fish from illness. Most of the fish can tolerate the amount you add for Mollies.

Salt for the aquarium must be pure salt. You can buy aquarium salt at the pet store. The salt must not have iodine like table salt does. Table salt is not apropriate for the aquarium.

6

Actually, “pure” is not what you’re looking for. HD is correct that iodized table salt is not good. But your best choice (also the most expensive) is aquarium salt, which is synthesized sea salt. It’s “clean,” but it’s the opposite of pure. Pure salt would be just sodium hydrochoride: one mineral. Sea salt contains many (hundreds? thousands? millions?) of minerals. It’s not just the saltiness the mollies need, it’s the minerals.

Sea salt sold for the table is adequate for your needs, and cheaper than aquarium salt. As long as there is no EXTRA iodine added–“non-iodized.”

7

One of the disturbing things was there WERE no symptoms. One day they were swimming around normally, the next day they were dead. (The smaller mollie did seem a bit antisocial but it was always shyer than the others.)

Y’know, these plants are doing really well. Java fern growing like a weed, sword spreading all over the tang & growing new leaves. This was all despite the mollies nibbling on them. Maybe I need to add more salt.

There is also a lot of algae in there, including algae growing on the plants themselves.

I actually had a hard time deciding if plants were the point or if fish were the point. But I think I feel much worse losing the mollies than if I had to fish some dead plants out of there–so I guess the fish are the point. And I guess I should go buy some more. I’m just worried that I’m putting them into a somehow toxic environment.

8

Don’t put them in until you have the problem solved.

9

Okay. The only thing I have come up with, though, is that the fish died the day after I changed the water. I have been changing about 1/4 of the water in the tank about once a week. While the tank was cycling last spring I changed about a gallon every day or two–whenever I could smell ammonia–but since early summer it’s been once a week. Now, I did lose all those baby mollies but they didn’t die, they just, um, disappeared before I could get to the store to get a net and get it in there to protect them (even though I had been told that mollies didn’t eat their young;well, I disagree).

When I change the water I also scrape algae off the side, and jostle the gravel as I siphon water out to try to get stuff out of the substrate. I’m not sure I will know if I have the problem solved.

10

Your right. I just didn’t want to have people blame me because they killed the fish with bad salt.

11

When your Mollies are about to give birth you can put them in a little enclosure in the tank. One type of birthing enclosure has two chambers and a connecting channel. Air bubbles on the babies side draw a current from the parent’s chamber. The fry get gently sucked through the channel into the baby part. It’s a good investment if you have live bearing fish.

12

okay, first things first, do you have any liquid water chemistry tests, the test strips are unreliable and beyond useless

the first thing i’m suspecting here are dangerous levels of nitrogenous waste (Ammonia/Nitrite/Nitrate), these compounds are invisible, water with a .50 PPM concentration of ammonia looks no different than water with no ammonia, but the first batch of water is dangerous to fish), a cycled tank should always have 0 PPM of ammonia and nitrite, and less than 30 PPM of nitrate to be safe

ammonia and nitrite are toxic in concentrations of .50 PPM and below
nitrate is not toxic to fish (except in large quantities) but is a plant fertilizer

the fact you’re getting algal buildup could indicate a couple of possibilities…
1; you have a large concentration of Nitrate, and not enough live plants, the algae is simply taking advantage of an available food source
2; you’re leaving the tank lights on for longer than 12 hours, increasing the photoperiod time only encourages algal growth, to have plants outcompete algae (which grows in almost any lighting, and is more efficient than live plants in a low light tank) you need to increase the light’s intensity and color spectrum (5500 to 9325 Kelvin)
3; the bulb(s) or flourescent tube in the tank hood/lightstrip is either the wrong color spectrum, or too old (most standard flourescent tubes exhaust their useful plant-specific wavelengths in 6 months, they’ll still illuminate the tank, but the color spectrum for live plants goes all wrong)

you should be doing weekly water changes no matter what, to get the nitrate out of the water, and to keep the micronutrient balance optimal, if the tank is heavily planted, you may be able to push water changes back to biweekly…

how many fish are in the tank now, aquariums should be stocked by the guideline of 1 inch of narrow bodied aquarium fish per gallon, make sure you use the adult size

for example, in a 10 gallon tank, you could have 10 narrow bodied Tetras (Neons or Head and Tail Light, they count as 1" of bioload per gallon), OR 5 Corydoras Catfish (2" of bioload per gallon), 3 Dwarf Pufferfish (each 1" puffer counts as 2" of bioload per gallon as they’re messy eaters), or 3 adult size mollies (3" bioload each)

to borrow a text block from another forum i hang out on, Aquamaniacs, please fill in this help text block…

13

okay, given that you were waiting for the tank to cycle, ammonia odor is part of the process, however in a cycled tank, if you smell ammonia, something is WAY out of whack, as i stated above, even concentrations of .25 to .50 PPM of ammonia are dangerous, and you can’t smell it at those concentrations…

i’ve rescued bettas from death-cups that have lethal levels of ammonia, and it amazes me that they survived without permanent damage, the worst example was Steel, a silver-gray-blue veilteil betta, his death-cup water was gray when i tested it, it tested OFF THE SCALE, the water turned an intensely dark green, it looked black it was so dark, it was darker than the darkest reference color (8 PPM)

as long as you don’t scrub the gravel clean with hot water or do other things to kill the nitrifying bacteria, you shouldn’t disrupt the cycle in the tank by gravel cleaning…

14

I do not have liquid testing stuff. Strips is the best I could do, although I can get the water tested at PetsMart, apparently. I asked some questions of somebody at PetsMart who (in the tradition of PetsMart) may or may not know what she’s talking about, who said sometimes fish just die. Well, okay. But quite aside from not wanting to torture fish, these are the pets of a 10-year-old kid, who names them.* I mean, yeah, he isn’t into prolonged mourning or anything. But…

*OK, I named the tetras. Larry, Daryl, Daryl, Daryl, and Larry.

15

You can get Ammoniacarb for your filtration system. That has a ammonia remover mixed with the carbon filtrate. You can purchase a mesh bag with the ammonia removing compound and drop it onto the gravel. It will remove ammonia, but not as good as when it’s in the filter. The bag that removes ammonia can be reactivated good as new at home. It’s a matter of doing what the instructions say.

16

  1. Ammonia/Nitrite/Nitrate? 0/0/20
    looks good, tank is cycled, water seems within spec

  2. pH/GH/KH? 6.8/75/40
    no problems here

  3. Temperature? 78-80
    this is also fine

  4. Tank size/Filtration? 10 gal, undergravel w/airstones
    personally, i’m not a fan of UGF’s (Undergravel filters), they can get a buildup of crud under the filter plates that can go anaerobic, create hydrogen sulfide gas, and kill off the tank occupants if you don’t clean under the plates on a regular basis (4-6 months), either by pulling the UGF out and doing a 100% water change (don’t scrub the gravel or you’ll kill the good biobugs and cause the tank to go thru another mini-cycle) or by sneaking some large-bore airline tubing under the plates (thru the uplift tubes) and siphoning out the built up crud, UGF’s are not good with live plants either, not enough grip to hold stem plants, and root feeders can clog up the filter plates with their roots

i prefer power filters, specifically the Hagen AquaClear line, powerful, quiet and versatile, but if you have your heart set on keeping the UGF running (not reccomended, power filters are much better), you can turn it into a “Power UGF” by purchasing a pair of inexpensive powerheads and sticking them on the ends of the uplift tubes you have the airstones in, it will make the UGF more efficient, and also reduce the chances of the plates going anaerobic

  1. Water change amount/frequency? 2 gal/weekly (or less often)
    you should increase the volume of water changes here (unless you live in an area with drought/water rationing, 25-50% weekly is the most effective amount, but more never hurts

  2. Water additives/Medications? dechlorinator, sea salt (at water change)
    salt is a controversial subject in freshwater aquaria, but mollies are one of the few species that do benefit from it, i’ve kept mollies in brackish conditions (1.15 salinity) and they thrived, they may in fact be closer to a brackish water fish than freshwater…

  3. What, how much and how often do you feed your fish? flake, little pinch, once/day

sounds good here as well, bewtter to underfeed than overfeed

  1. Tank inhabitants? 1 gold molly, 5 neon tetras, 2 plants & a rock

okay, using adult size, you have…
1 gold molly (adult size 3")
5 tetras (5" total)
8" of bioload in a 10 gallon tank, i.e. 8 gallons of bioload, you’re on the high side of being understocked, but are still understocked, i would not add any more fish at this point, better to be understocked than overstocked, and seeing as your UGF is a liability, play it safe…

  1. Any new fish added to the tank? Who and when? Not since August (babies)
    good, no bioload increase

  2. Any unusual behavior or symptoms? 1 of the deceased mollies seemed shyer (i.e. harder to find) than usual (many hiding places in tank)
    before it died, did it exhibit any other strange behavior, clamped fins, loss of color, erratic swimming habits?, these are all signs of stress, has the tank been chilled recently, perhaps an extended power outage caused tank temps to drop?

  3. How long has the tank been in operation? April (?–possibly early May)
    if you haven’t siphoned out the crud from underneath the UGF, do so ASAP, there’s almost a year of built up crud and mulm under the UGF plates, possibly gone anaerobic, ideally, ditch the UGF and get a HOB (Hang On Back) power filter like the AquaClear, at the very least scrap the air pump and airstones and replace them with a pair of powerheads

17

oh one final thing, when you keep an aquarium, you really need to keep an eye on water parameters more than the fish, in all honesty, you don’t really have pet fish, you really have “pet water”, that just happens to have fish and plants in it, so take good care of your pet water and the fish and plants will be happy as well

18

Hilarity N. Suze
Enjoy the aquarium and don’t get discourged by people here. It’s just a couple fish. I’d swear you were beating there kids.

19

(Nott deletes his lame mollycoddling joke)

20

AskNott, thanks for deleting your lame joke, as these mollies are (were) definitely not being coddled.

MacTech, interesting site (aquamaniacs). I had NO idea there were so many things that could go wrong with fish. I found another semi-interesting place except it seems to be infected with a bunch of pepl who rite lk ths. So I need a translation.

I have received a bunch of conflicting information from various sources and now am thoroughly confused. I have been told not to change the water so often and to change less of it, to change the water MORE often, to use a water purifying chemical, above all else NOT to use a water purifying chemical, etc. The fish experts have suggested the mollies might have had internal parasites and recommended Jungle Parasite Clear, but said I should remove all the activated charcoal in all the filters before using it.

So, one treatment so far, and I now have GREEN WATER, very green, very murky water. I added a new powerfilter and cannot figure out how it could be responsible for this pea soup, but if it’s not the powerfilter then it’s the parasite clear.

Through the murk I can barely see the fish, but Big Gold Molly appears to have a couple of black spots. They were not there in October, when my kid took a bunch of pictures (I couldn’t remember if he had black spots when we got him, but apparently not). The skin around his head is looking a bit pale and scaly, too.

One thing that was true of all the mollies–those that perished and the survivor–is that occasionally they spend a lot of time snuggling up to the heater in the tank. Just hanging out real close and not moving, appearing to snack on something (hidden algae?). Big Gold is still doing this, although not all the time.

But no deaths for a couple of weeks (knocking wood here).