Could medications stunt fry?

[AdoraBelle Dearheart]

I have two guppies from a small batch that were born July 30th, so they're three and a half months old. One male, one female. They seem fully mature, male coloured up and courting females, but one thing... they're tiny! About the size of fry that are 1-2 months old. Usually, my guppies would be adult size by this age, even though the males usually keep growing their fins out until about six months, they're still larger than this is body size.

The female and male. They seem healthy and active and well, just small.

The male next to his dad really shows the size problem. The mother was a normal size too.

The platy isn't even fully grown, about four months old, but dwarfs these tiny guppy youngsters.

Tank isn't overcrowded, parameters are great, and they seem healthy. I had to battle worms in the tanks when these were only two days old though. I wonder whether the medications could have stunted their growth? I can't think of another reason for them to be fully mature, yet so small, otherwise! Anyone ever experienced or heard about something like this?

 

[Colin_T]

lack of food
lack of water changes
cool water

 

[Ch4rlie]

Hmm, interesting question to be fair.

Medication does undoubtedly have an affect on all livestock in the same tank that's being treated, usually for the better if fighting parasites and worms etc but for growth in fry, I am unsure.

It may well be the case but without scientific proof and having a quick search google search I cannot say for sure.

As Colin T says, feeding, and lack of water changes can certainly have an affect on fish growth, I do not know if cooler or warmer tank waters will affect growth as that too is an interesting hypothesis imho.

 

[fish48]

guppies do well in cooler water - between 68f and 72f they grow slower but not stunted usually becoming a stronger fish and live longer

 

[AbbeysDad]

First, anything and everything in the water gets into fish through osmosis.
I believe that meds can stunt the growth of fry, but there may be genetic factors (sometimes going back many generations) and as pointed out food, water quality and temperature are all factors.
It would only be guessing as to the exact root cause for these smaller fish.

 

[AdoraBelle Dearheart]

Tanks are maintained at 76-77 degrees F, and I feed a minimum of twice a day, usually 3-4 times a day when fry are small, and I do large water changes religiously. Minimum of weekly with the current stocking, but with say, the fry tank now that has 37 guppy fry and fed often, it's 2-3 times a week, 75% water changes.

The two above were the only two survivors from a small batch, perhaps suggesting there might have indeed been a genetic issue? However it was that females first batch, so I expected small, plus born in a community tank so adult predation could have accounted for losing some too, I don't know how many she had. Her second batch she had 38, which seem to be growing normally without any changes to my usual methods, and I've raised a few hundred guppy fry before without this issue.

These two have been raised for most of their lives in an lightly stocked 15.5 gallon, containing two adult guppies, four sub adult platies, and red cherry shrimp. Plenty of space, heavily planting, regular water changes, and lots of filtration too. Nitrates usually 5-10.

I can't think of any reason for them to see mature and healthy, yet so small at this age, except the medications when they were still so tiny.

I didn't really have much choice though, I was losing fish to the worms, and couldn't delay treatment any longer, especially since by the time these two were older, another batch would have born, and the cycle would continue. Unless I'd moved these two to an isolated tank with no shared equipment, and treated them when they were older, and hoped the worms hadn't been transferred to them yet. But the worms were killing fry that were between 1-2 months old, so hard to say if that would have helped.

I'll keep these two in male/female only tanks, they can live out their lives here. At least they appear to be healthy and normal otherwise, just very small compared to normal guppies.