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Should I skip water changes?

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This morning I went to WM and got a gravel vac, a bucket, and fish pellets. Was able to vac the bottom; it was a lot easier. I will not worry about them eating any more though. I feed three times a day and got just some poo up with the water. Was not much at all. Got a diff brand of pellets. they did eat these tetramini, floats but after a min they sank. the bucket holds @ 4 gallons so probably took 3 out. Only a little got on the carpet. Was a lot smaller amount than i generaly take out, might make it an extra change and still do a big one on thursdays. Fish were scared and did not stop coner hiding until i put in a pich of flacks. My moore did not get sucked in though, which he does with the jug. Hope they get use to it and are not to upset. Think i will try the pellets at morning, the flacks at night, and either blood worms or shrimp for lunch. Does that sound like a good plan?

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I'm not going to get into the growth hormone debate as it is 50/50 in goldfish, and the fact remains that either way lack of space, filtration and water changes results in stunted, sickly fish. regardless of the exact mechanisms, it happens.

However, I am going to get my back up on one point (nothing personal, but it needs to be said! :) ) in particular because I, as someone previously keeping koi, am sick and tired of hearing this one over and over again.

To date, as far as I can tell there are no scientific papers supporting the existence of a specific substance that is produced by a fish and inhibits the growth of that species of fish -- not in goldfish, not in koi, not in any other species.

Heres the newsflash and the research we have had since the 1930s for koi. Growth hormone and gonadotropin secretion in the common carp (Cyprinus carpio) and koi (this has been repeated in them) can and do stunt growth. Pick up any aquaculture journal from that era and have a flick through, you’ll find at least one well written peer reviewed article for it with research to back it up. Unfortunately this is all pre internet and their no real aquarium journal database, and what little is archived is in commercial fishery journals so I rarely see people going to look in the right place. Hell, for koi, we even have the type/family of molecules (though not the exact ones!) isolated and identified. Gonadotropin-releasing hormone (sGnRH) agonist [D-Arg6, Pro9NEt]-sGnRH (sGnRH-A) growth hormone (GH) (which, newsflash is an isolated and identified number of exocrine compounds in koi that collectively restrict growth! But the exact formation/hormone varies in other species, naturally) and gonadotropin (GtH), so on and so forth ALL affect the growth or koi, other fish and, in fact, goldfish too.


These are common carp, not koi, but the experiment holds in koi. Fish in vitro were tested with the hormones extracted from salmon, but that’s not the interesting part for us. What’s interesting is the actual experiment itself was testing substances on koi to see how much of an increase in their growth hormones (both stunting and promoting ones) they produced. The hormones produced and their supposed effects were measured. I thought I’d use this as it ties in nicely with what has previously been said about this research being good for large scale breeding projects, because there is a lot of it out there, and it’s very well funded.

You can debate it for goldies, I myself are on the fence about it as I am yet to see significant research into it into goldfish, but it is plausible for sure. However, there are buckets of evidence for it in koi with some of the compounds actually known, so please be aware of that when debating this. Saying koi ‘don’t do it’ is not right given there is evidence for it.

Get onto these if you need further reading :)

Sprenger, Kappy. 1974. Growth Inhibiting Secretions. Colorado Aquarist. Jan. 1974. Reprint of the original from San Francisco Aquarium Soc.

Stacey, N.E. Role of hormones and pheromones in fish reproductive behavior, An evolutionary perspective. Prentice Hall, Inc. Englewood Cliffs, N.J. 1987, pp. 1-350.

Anon. 1988. Stunt Work. T.F.H. citation of Daniel Heath and Derek Roff, "Test of Genetic Differentiation in Growth of Stunted and Nonstunted Populations of Yellow Perch and Pumpkinseed". Transactions of the Am. Fish. Soc. [116(1):98-102]

(that one is non carp, but a good read!)

Drickamer, L.C. Pheromones: Behavioral & Biochemical Aspects. Adv. Comp. Environ. Physiol. 3, 1989, pp.269-348.

Many use koi, common carp, or other carp as the experimental fish. Some of these also give indication for a similar phenomena in goldies, ie, cysteamine being used to induce growth (article- cat.inist.fr/?aModele=afficheN&cpsidt=15337401) and so on. Some tests show that it may bind with the GHs, therefore neutralising them so they no longer inhibit growth. Since goldies also have increased growth (similar to fish being kept in a flush system where water is constantly changed/dripped out and in) when under the same conditions, a similar phenomena is probably happening, where the cystea blocks the GHs. Also given the genetic closeness of the fish it is highly likely that goldfish, like almost all carp, produce GHs.

Why do you see no research on it now a days? In koi an most other fish it’s a topic that was settled YEARS ago, guys :P. All of these books and research is 1970-80s If you can get your hands on them, some even LIST the compounds identified as growth stunters, and which ones the fish naturally produces.

In goldies though, it’s not just the hypotheticial GHs that do this, low oxygen and high waste also contribute hugely, but don’t rule it out just yet. However when it comes to koi, in face of the research I would be doing research before saying it is a fabrication. :)

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And in addition a quick google search actually bought a bunch of research on this up.


Growth Hormone and Gonadotropin Secretion in the Common Carp (Cyprinus carpio L.): In Vitro Interactions of Gonadotropin-Releasing Hormone, Somatostatin, and the Dopamine Agonist Apomorphine


Characterization of growth hormone binding sites in the goldfish,Carassius auratus: effects of hypophysectomy and hormone injection

A recombinant carp growth hormone (rcGH) was used to develop for a GH radioreceptor binding assay in the goldfish (Carassius auratus). Specific binding of125I-rcGH to goldfish liver membranes was a pH, time, temperature, and membrane protein dependent process.

(Use of artificially manufactured carp GH –rcGH- on Goldfish shows that goldfish have receptors for GH. It’s a cloned GH, to whoever was asking before. There are MANY of them out there.

Stone, N., Mc Nulty, E. & Park, E. (2002) "The Effect of Stocking and Feeding Rates on Growth and Production of Feeder Goldfish in Pools" North American Journal of Aquaculture, Vol. 65, No. 2, pp. 82-90.)

Is a modern one that delves into it very deeply.

Yunker, Lee, Wong, Chang (2000) Norepinephrine Regulation of Growth Hormone Release from Goldfish Pituitary Cells. II. Intracellular Sites of Action , Journal of Neuroendocrinology, Vol. 12 (4), pp. 323–333.


Previous results suggest that norepinephrine decreases growth hormone (GH) release in goldfish by means of α-2 adrenoceptor activation. The intracellular mechanisms by which norepinephrine inhibits GH release were examined in the present study using dispersed goldfish pituitary cells. In 2-h static incubation experiments, norepinephrine and the α-2 agonist clonidine decreased basal GH release and the GH responses to stimulation by the dopamine D1 agonist SKF38393 and two native gonadotropin-releasing hormones (GnRH).


The inhibitory effects of g-aminobutyric acid (gaba) on growth Hormone secretion in the goldfish are modulated by sex steroids

INTRO- Growth is seasonally regulated in goldfish, and the highest growth rates are found in the early summer after the spring breeding period (Marchant and Peter, 1986). Growth hormone secretion from the goldfish anterior pituitary also varies seasonally (Marchant and Peter, 1986; Trudeau et al., 1992). Serum growth hormone levels increase during gonadal development in late autumn and winter, a time when somatic growth is lowest (Marchant and Peter, 1986; Trudeau et al., 1992). This increased release of growth hormone probably acts in concert with gonadotropin-II (GTH-II; the luteinizinghormone- like molecule in fish) to stimulate steroidogenesis (Van Der Kraak et al., 1990; Le Gac et al., 1993) during seasonal redevelopment of the gonad. The control of growth hormone release involves both stimulatory and inhibitory mechanisms. Growth hormone release in the goldfish is stimulated by bombesin (Himick and Peter, 1994), dopamine (Chang et al., 1985, 1990; Wong et al., 1993), thyrotropin-releasing hormone (TRH; Trudeau et al., 1992), neuropeptide Y (NPY; Peng et al., 1993), growth hormone-releasing hormone (GHRH; Vaughan et al., 1992), gonadotropin-releasing hormone (GnRH; Marchant et al., 989a), cholecystokinin (Himick et al., 1993) and pituitary adenylate cyclase-activating polypeptide (PACAP; Wong et al., 1998). In contrast, growth hormone release is inhibited by insulin-like growth factor-1 (IGF-1; Weil et al., 1999), norepinephrine (Chang et al., 1985), serotonin (Somoza and Peter, 1991) and somatostatin (SRIF; Marchant et al., 1987). Interactions among these stimulatory and inhibitory neuroendocrine systems drive seasonal cyclicity in serum growth hormone levels (for reviews, see Peter and Marchant,1995; Trudeau, 1997).

This is a good one as it talks about growth PROMOTING and growth INHIBITING hormones (both are secreted it seems, and which is varies on enviroment)


A review of chemical communication in freshwater fish

Since communication between individuals of a species of fish by chemical agents (pheromones) was first demonstrated in 1932, such a process has been suggested in many aspects of fish behavidïo'ur and development. This review describes observations on such mechanisms in shoaling behaviour and beneficial conditioning of water, homing of migratory fish, communication of alarm, ‘crowding factor’ (which adversely affects growth, survival and fecundity in dense populations), pair formation and spawning, and a range of other social interactions. Some of the chemicals involved have been isolated and identified, but most are indicated by behavioural observations. Pheromones are of great significance in fish behaviour and ecology, and are likely to be an important factor in culture operations.

I found all of these in 5 mins. Looks like there is actually A LOT of goldfish related research out there. I’m going to delve deeper later.

My own experience suggests that water changes have a huge effect on growth. But diet, temperature and stress will all play a part along with the fishes own genetics.

It's not an easy subject and the deeper you go the more complicated it gets.

Edit: whoever asked why we on't have a cloned/isolated growth hormone. We do have one, it's called rcGH (Recombonant Growth hormone)

I think its facinating, I plan to read further after I finish uni for the semester (swamped with other journals at the moment!

Edited by Amber

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i think that you must have to change it weekly because there are the lot of bacteria produce in the tank...which is very dangerous for the fishes so that you must have to change it safely means you have to change it weekly minimum 50% of water change weekly.thanks

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Bacteria etc. aside, think of the poop that always collects in the bottom of a tank or in the filter! Larger solids take longer to break down, and I know most people here will have seen them collecting around the tank (or if you have gravel they are there and you just can't see them). It's like never hoovering or sweeping up after a dog or cat that sheds a lot of hair, it gets everywhere and doesn't go away on its own, it just builds up and builds up. Water changes are a good way to get rid of this muck from your tank, and roughly once every 4-6 weeks from your filter to keep everything sweet, it's like weekly housekeeping on your tank :)

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Very interesting research Amber! Now the question becomes, for those that WANT to keep their goldfish small, is there a way to clean the waste out but leave in the restricted growth hormone(maybe one of those Eheim Gravel Vaccums that just filters and returns the water to the tank), ideally after a few generations, this could lead to true 'dwarf' goldfish

Think about the possibilities, 1"-2" healthy full grown comet goldfish, goldfish that can actually be Kept in the tanks that are sold for goldfish!

Edited by Ridewithme38

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That would be pretty neat Ride! I know we have the reverse, there are substances for koi like the cysta that neutralise the ‘bad’/inhibiting hormones while promoting the ones that cause growth.

From the abstracts I think it looks interesting, after I finish my assignments and exams for this semester I think I’ll delve into it properly, might even do a research submission for here or something if I find definite results. :)

Breeders often tell me that once goldfish reach a certain size (approx. 4 inches body length I believe it is for fancies, and longer/8inch for commons) even if they are stunted after reaching that size by GH because their bodies are fully developed it’s not such a bad thing. The hypothesis is that in the wild that’s how the GH would probably work, ie, once the fish are adults they would keep growing until reaching full size or the saturation of GH caused them to stop. In our tanks though with the large amounts of inhibiting GH, the waste build up and low ammonia we stunt young, growing fish (when usually they would not be saturated with thee hormones) and cause them to have lifelong problems. It’s when they are growing and developing for the first few years that it can really cause lifelong problems/disease prone fish. It's why koi, once sexually mature and a certian size, if stunted AFTER that (not before) can live quite happily for ages/a comparable lifespan to non stunted koi.

There are goldies that are naturally rather tiny when fullgrown, like the chinadoll telescope line that in some specimens top out at only a few inches. :)

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