Re: [RML] rainbowfish goiter

Bruce Hansen (bruceh at
Wed, 25 Jul 2001 06:00:49 +1000

I think you are right Tyrone , in that Iodine generally is found as a trace
element in most environments and that there are very few areas in the world
where there is so little of it that deficiency states (causing goitre) can
develop. My understanding is that Iodine is a necessary component of
Thyroxine and other Thyroid hormones which animals produce to control their
metabolic rates.

If the animals receptors detect a deficiency of Thyroid hormones then a
feedback reflex stimulates the Pituitary gland to produce Thyroid
Stimulating Hormone which then normally increases the production of
Thyroxine etc.During the process each cell may increase slightly in size.

If this fails to increase the availability of Thyroxines then the increased
amounts of TSH cause the Thyroid gland to produce more thyroid cells which
then increases the bulk of the Thyroid gland and it becomes visually obvious
and is then called a "goitre".

I am not sure whether supplying iodine will totally reduce the size of the
goitre until it is no longer obvious. However it should restore the
metabolism of the fish to normal and allow them to feel well again. The
important thing to remember is that raising fry in your iodine-deficient
conditions needs to be allowed for.

One of the things we forget when we raise fry in small volumes of water as
compared to nature is that the rapidly growing animals use up minerals and
nutrients from the limited volume we supply them with. If any element is in
limited supply then deficiency states may result - this goes for trace
elements especially and perhaps adding a small amount of marine trace
element drops regularly may help. In nature , even in very low TDS waters
the water movement, and the sheer volume not only provides supply but also
removes metabolites which may act as growth retardants.

Bottom line message - perhaps some shell grit in each fry tank, frequent
small water changes, and perhaps trace element supplements ?

Bruce ( Hansen )
vicepresident - ANGFA Inc (
- ANGFA (Qld) Inc (

----- Original Message -----
From: "Tyrone Genade" <Tgenade at>
To: <rainbowfish at>
Sent: Monday, July 23, 2001 8:09 PM
Subject: Re: [RML] rainbowfish goiter
> I don't use an iodine mix or any salt mix with my
> Tanganyikans. All I know is that of all the 'bows I've
> raised in the tank so far none have developed any goiter
> etc... No doubt there are iodine traces in the shell
> gritt etc...