How do I know if a fish is old or sick? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 4 Old 04-06-2014, 07:40 PM Thread Starter
How do I know if a fish is old or sick?


In the past 2 months I have lost 3 fish (about 2-3 weeks between each one) - all of which I got from the pet store about 8-9 months ago.

Two different breeds (2 glofish and 1 Molly)

All over a period of weeks stopped being so aggressive at feeding time and all started mostly just hanging around at the bottom of the tank looking for left over food. With the glofish I could see that they were losing weight but otherwise looked ok.

All other fish in the tank are looking and behaving normally.

Ammonia 0
Nitrite 0
Nitrate 20-40

I think the fish just got old...but I want to make sure that there wasn't something I was supposed to do when I saw them start to be less aggressive with eating.
Could there be a disease in the tank I am not aware of? No unusual markings on the fish - all fins looking good.

How can I tell if they were sick or if they just were getting relatively old (don't know how old they were when I bought them)

What do you guys think?

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post #2 of 4 Old 04-06-2014, 09:45 PM
Sylverclaws's Avatar
It's possible you could have an internal parasite. Especially if they're eating well, but are still getting skinny and are hungry, and then dying off. Try feeding them twice a day and see if that helps. I've found feeding them once a day, they're usually absolutely ravenous by feeding time, and not all get what they need because everyone is starving.

As for knowing age: This is difficult. You never know how old fish are at shops, usually they have juveniles, fish that are 5-8 months old, but sometimes they do give away much older fish. Providers often give away their breeders once they've had them around for a couple years.

Sometimes they will be a bit slower and look a little gaunt, but they don't just drop weight like you're talking about, not usually.

I recently had a swordtail who passed of old age, he was a bit slower, but otherwise got around ok and ate well, who passed away. Just went to sleep in his little place between my plants, looked normal until I realized he wasn't moving to come for breakfast. Not all get this way though, some never really show much age, but just die like that for no apparent reason.

Turning on the Aquarium lamp in the morning is MY cup of coffee.
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post #3 of 4 Old 03-01-2015, 05:45 PM Thread Starter
So, when I see one of the fish start to become less active, is there something I should be doing to help it recover?

Put it in its own tank or something?

The general pattern I see is that they will first start hanging out in the tank corners, then they start to eat less, then they they start to struggle to breath and then die.

Is this anything that can be reversed in some way?

I have been assuming that this is a natural death, but I am not sure.

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post #4 of 4 Old 03-02-2015, 08:38 AM
Sylverclaws's Avatar
Hanging out in corners struggling to breathe isn't normal. Lack of oxygen in the water is what it sounds like, or some serious stress. From what I can't say. Could be a number of things from other fish bullying it, to water stats bouncing or being off. Temp is wrong....adding in water too hot or cold during changes, or changing too much can shock them and stress them out.

From your first photo I can tell you your nitrates are high, that's not good for them. You want it below 20, 0 is best but they can usually handle it up to 20.

Mollies like warmer, harder water than glofish do( need temps 78-82F GH 15-30, in between there is the best, they like it hard, PH 7.2-8.0, KH 25-40, nitrite and ammonia need to be zero, nitrate should be under 20ppm. For tetras, the black skirt ones that have been modified: prefer temps 75-80F, KH 5-10, PH: 6.0-7.5 GH, 5-20 they like it much the zebra danios are a bit different, they like it cooler between 70 and 75 degrees, PH: 6.5 - 8, water hardness between 5 and 25 degrees, KH: 8-12) and like glofish need room and a group of four or more(I believe it's five or more for glofish). Without proper space, water stats and a group you'll having nothing but stressed out fish.

Mollies typically live 3-5 years as do black skirt tetras(they are usually the wider bodied glofish, danios are the longer more torpedo shaped ones), but danios(zebra danios to be more specific are the genetically altered glofish ones) can live 4-6 years I believe....however, glofish are genetically altered fish for that look and are not anywhere near as healthy as the originals, so I do not know age average for them, but I'd guess it's similar or less than mollies.

So make sure all your stats are where they should be and that you have the right critters with each other. The wrong type of water can really mess them up, and what's more, mollies like brackish water and neither danios or tetras will appreciate that. lol

Temp being off is you're most likely culprit for any molly issues, they like it hot and if it's not it freezes their metabolism, making them slow, not hungry, and what they did eat may rot in their bellies eventually killing them.

Turning on the Aquarium lamp in the morning is MY cup of coffee.
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