Cause for concern?

[Byron]

My view on the temperature. If the danio is the Zebra Danio (Danio rerio) it needs cooler water, the suggested range being 18-25C/65-77F. Most species of "danio" are similarly active fish, so similar lower temperature requirements.

The Bolivian Ram, Mikrogeophagus altispinosus, occurs in the Rio Guapore and Rio Mamore systems, Bolivia and Brazil. It is found in slow-moving streams and still waters (ponds). The water parameters in one habitat were measured at < 6 dGH, pH 7-7.6, temperature around 27C/81F. I kept my male Bolivian for over nine years in a temperature of 25-25.5C/77-78, which was well past the normal expected lifespan of 4-5 years; unlike its cousin M. ramierzi which must have warm water (82-86F/28-30C, this species does not demand this.

Angelfish that are wild caught require high temperatures, same as M. ramirezi and discus. Commercially-raised angelfish, which these in this thread I assume are likely to be, are like the Bolivian, fine at 25-26/77-79 but can have it warmer.

From this, I agree that a somewhat lower temperature would probably best serve the fish. Temperature drives the fish's metabolism, and the higher the temperature the higher the metabolic rate, which means more energy, burning the fish out sooner, adding stress...you get the picture. But the danio is the only real concern here so far as temperature.

 

[Ch4rlie]

I've never had Nitrite reading in this tank - it's always been zero (mature, established tank) and I feed sparingly. The other 3 mollies are much younger (fry from one of these, roughly 5 months old) and have 100% of their color. This tank has been disease free for over a year - no fin rot, ich, bacterial infections, bloat, popeye etc. No other fish in the aquarium has any discoloration on their gill plates or any other part of their body. These two mollies were swimming erratically, but not gasping. I'll take another Nitrite reading tonight for due diligence (and do their postponed water change/gravel vac)

It was only suggestion that the symptoms of red gills and faded colours could be down to nitrite poisoning but from your answers, one would have to conclude your other fish stocking would be showing signs of this also.

It seems rather odd to be perfectly honest. Were the mollies that passed away, were they being harassed by either the angels or the ram?
These are known to be aggressive in certain situations.

Just thinking could it be stress that killed them?

Or possibly as others are suggesting that the temperature of tank water is at the end range of molly optimum temperature 70-82F (21-28C) according to seriously fish but imho that’s not conclusive either.

Poecilia sphenops – Short-finned Molly/Black Molly — Seriously Fish

www.seriouslyfish.com

But otherwise don’t have much other options at this point am afraid.

 

[kribensis12]

My view on the temperature. If the danio is the Zebra Danio (Danio rerio) it needs cooler water, the suggested range being 18-25C/65-77F. Most species of "danio" are similarly active fish, so similar lower temperature requirements.

I kept my male Bolivian for over nine years in a temperature of 25-25.5C/77-78, which was well past the normal expected lifespan of 4-5 years; unlike its cousin M. ramierzi which must have warm water (82-86F/28-30C, this species does not demand this.

Angelfish that are wild caught require high temperatures, same as M. ramirezi and discus. Commercially-raised angelfish, which these in this thread I assume are likely to be, are like the Bolivian, fine at 25-26/77-79 but can have it warmer.

From this, I agree that a somewhat lower temperature would probably best serve the fish. Temperature drives the fish's metabolism, and the higher the temperature the higher the metabolic rate, which means more energy, burning the fish out sooner, adding stress...you get the picture. But the danio is the only real concern here so far as temperature.

Nailed it on the danios - Zebra Danios. I'll bump the temp down to 78. I must confess that I skimmed temp requirements for Bolivian's when I purchased this guy - I made the general assumption that they required warmer water and I know that commercially bred Angelfish seem to have a wider range of temperatures they can handle, so I thought 82 would be a good place to keep it.

It seems rather odd to be perfectly honest. Were the mollies that passed away, were they being harassed by either the angels or the ram?
These are known to be aggressive in certain situations.

Just thinking could it be stress that killed them?

I don't believe stress is a factor. All of the mollies are female, so there is no male to stress them out.

The angelfish are maturing, but don't bother any other tankmates - they don't really even both each other. That's not to say that it couldn't be happening when I'm not around, but I've never seen any aggression or signs of aggression (damaged fins etc.)

The Bolivian has never shown signs of aggression - he just hangs out in the bottom 3rd of the tank pretending that none of the other fish exist. He is very much a lone wolf.


Summary of responses that I am seeing (please correct me if wrong):
It's not likely to be a water quality issue or an aggression issue. What seems "most" likely is that it could be a combination of age and temperature.

Is my summary correct?

 

[Bruce Leyland-Jones]

What seems "most" likely is that it could be a combination of age and temperature.

Is my summary correct?

I'd have to say 'no', simply because the fish aren't old enough. The temperature may have been at the extreme end of tolerance for the fish, but not enough to actually kill them in the way you've described.

 

[kribensis12]

I'd have to say 'no', simply because the fish aren't old enough. The temperature may have been at the extreme end of tolerance for the fish, but not enough to actually kill them in the way you've described.

Do you have any other suggestions? That summary was based off aggregate feedback that I have received on this thread so far.

 

[Bruce Leyland-Jones]

Do you have any other suggestions? That summary was based off aggregate feedback that I have received on this thread so far.

I know and this is a problem trying to diagnose an issue long gone.
That said, whilst your fish may have shown signs of nitrite poisoning, then I would also have expected your other fish to have exhibited similar issues...but they didn't.
Personally, I'm not comfortable with the temperature they were in, but this hadn't been changed prior to the deaths and it was within their 'tolerable' limit. Whilst not seeing this has the main cause of death, I'll concur with @Byron 's comments on temperature above, particular with regards stress levels.

I'd be more closely drawn to possible aggression from the other fish, likely occurring after lights-out and, therefore, unseen. If I had to point a finger, I'd say the Butl...er...the Angels did it.

 

[AdoraBelle Dearheart]

I don't believe stress is a factor. All of the mollies are female, so there is no male to stress them out.



Summary of responses that I am seeing (please correct me if wrong):
It's not likely to be a water quality issue or an aggression issue. What seems "most" likely is that it could be a combination of age and temperature.

Is my summary correct?

I don't think anyone believed that age is a factor, correct me if I'm wrong?

Two years really isn't even slightly old for mollies. Even the five years given as a usual average life expectancy is an underestimation in my opinion/experience with mollies, but even taking 3-5 years as an average, two is not elderly. Mollies aren't like guppies, where two years is a much more common lifespan for a pet store guppy.

Did you get these mollies from a store? How long have you had them?

 

[AdoraBelle Dearheart]

Sorry, I meant to add that even if their age were in question, the fact they died in the same week strongly suggests that old age wasn't the cause.

I don't know what the cause is, I'm sorry. But I think there's a danger in chalking it up to old age, then not uncovering a real problem.

 

[kribensis12]

Whilst not seeing this has the main cause of death, I'll concur with @Byron 's comments on temperature above, particular with regards stress levels.

I'd be more closely drawn to possible aggression from the other fish, likely occurring after lights-out and, therefore, unseen. If I had to point a finger, I'd say the Butl...er...the Angels did it.

Correct me if I am wrong - but I was under the impression that mollies and angels were very compatible. Is this not the case? It's true that I don't see what goes on when I am not there, but no fish has shown an ounce of aggression or conversely, any sign of damage. While I may never know (unless more deaths occur - hope not!) what their cause of death was, I'm having a very hard time believe it was the angels. Obviously they are cichlids and if they really wanted to, they could attack and kill a wide assortment of fish.

I don't think anyone believed that age is a factor, correct me if I'm wrong?

Two years really isn't even slightly old for mollies. Even the five years given as a usual average life expectancy is an underestimation in my opinion/experience with mollies, but even taking 3-5 years as an average, two is not elderly. Mollies aren't like guppies, where two years is a much more common lifespan for a pet store guppy.

Did you get these mollies from a store? How long have you had them?

Others seem to be correlating temperature with increased aging of the fish.

I bought them at the LFS about 9 months ago. When I purchased them they were already maxed out on size for a female and heavily pregnant. Their fry are about 5-6 months old and are not as big, so I was estimating at least 2 years but there is no way of knowing for sure. The first one started to loose it's color over the past month or more (I sorta think it started in June, but I didn't document it) and the second one with a week or two.

I'm kind of reserved to not knowing what caused these deaths, but will make the recommended temperature change and keep a closer eye on the interactions between the angels and their tankmates. Hopefully I do not loose any more and if I do, I may have to make some tank adjustments.

 

[Ch4rlie]

I bought them at the LFS about 9 months ago. When I purchased them they were already maxed out on size for a female and heavily pregnant. Their fry are about 5-6 months old and are not as big, so I was estimating at least 2 years but there is no way of knowing for sure. The first one started to loose it's color over the past month or more (I sorta think it started in June, but I didn't document it) and the second one with a week or two.

This is now making me think it’s more related to do with age.

If you estimate the mollies to be at least two years old since already maxed out in size and gravid at the time you purchased them. Then they could have been older as it’s pretty hard to determine age of any specie of fish imho. They could have already been at least 3 or 4 years old at that point, no idea tbh.

So with that in mind and also having the temperature at their maximum range means their lives is likely to have been shortened as the high temp increases their metabolism and this in turns adds pressure/stress to their bodies.

In my humble opinion I’m beginning to think this is the case, it may be likely to be linked to age and temperature as no other livestock seems to have been affected otherwise these other livestock would all be showing signs of ammonia/nitrite/nitrate poisoning or similar if was other type of water parameter issue.

 

[kribensis12]

Update: No more fish loss, all female mollies seem to be 100% okay and no other fish has any symptoms. Water quality is perfect. So I'm thinking that whatever the cause of death was, it is no longer a concern.

 

[Ch4rlie]

Update: No more fish loss, all female mollies seem to be 100% okay and no other fish has any symptoms. Water quality is perfect. So I'm thinking that whatever the cause of death was, it is no longer a concern.

Fingers crossed and hope for the best.