Discus growth and rocks

[Week End]

Has anyone heard of certain types of rocks will leech stuff into your tank and make your discus not growing?

or any other issues other than inadequate feeding, small tank and deformed specimen that makes discus don't grow?

[Merrilyn]

Hi Weekend, now that question has got me thinking.

If good food, clean warm water, and plenty of water changes encourage growth in young fish, then lack of all those things will hinder growth. However, as in most things in nature, I believe there are such things as "runts" in fish, and no amount of good feeding and good care will increase their size.

I recently did an experiment with a snakeskin spawn of my own. I normally cull spawns fairly heavily, so that only the strongest and best shaped fish are grown on. Any that fail to thrive early on are usually culled from the spawn, but this time I deliberately allowed them to grow, even giving them their own separate tank, away from their more vigorous brothers and sisters.

Despite identical conditions, at the end of twelve months, they were less than half the size of their siblings. All had a stunted appearance and huge eyes.

Now, whilst this is far from a scientific study, it has been sufficient to prove to me that some fish simply do not grow and thrive, despite the best care.