Growth Inhibitor Hormones and Carbon

[Potts050]

I've noticed that while raising both trout and tropical fish fry that there is considerable range in the size and growth rate of fry within the same brood. While it is obvious that some fish feed more agressively than others and would therefore be expected to grow faster there appears to be other factors at work.

If the frequency of water changes and the volume changed is increased then there seems to be less differance in brood size and a generally faster growth rate. This has been explained by the presence of growth inhibiting hormones being released by fry and fingerlings to retard the growth of their siblings and the competition for food as a result. I have found a lot of info on the .net about research into growth hormones in fish but nothing on how to remove them. If your raising fry, you dont want anything to slow them down.

The problem is that when it comes to hormones, a little goes a long way. I read once that animal sensitivity to testosterone works at a level of concentration equal to dissolving a single granule of sugar in an olympic sized swimming pool! To remove the effect of GIH completely, you would need constant water changes.

This brings me to the carbon question: Will good quality activated carbons remove GIH from tank water and if so, how often will it need to be changed?

 

[fishfreak317]

nah i don't think carbon will remove it. i believe the only way is with WC's.

 

[rallysman]

I rely on water changes.

 

[necrocanis]

I find that very interesting. Would it work the other way if say you were to introduce fish growth hormone into the same water? Would it counteract the effects, and cause more fish growth? Kinda like fish steroids I would think.

 

[Potts050]

I find that very interesting. Would it work the other way if say you were to introduce fish growth hormone into the same water? Would it counteract the effects, and cause more fish growth? Kinda like fish steroids I would think.

I would think so but what hormone do you use and here do you get it?

 

[Mr.Firemouth]

The hormones need to be ingested to work. Many commercial feeds like the one that I buy by the ton have some type of growth stimulant in them. Whether it is just the make up of the food or an actual hormone is unknown.
Drip systems are used in hatcheries and fish rooms where fresh water is dripped in at 25g per day to 75g per day and the overflow water is piped to a drain. This allows for the constant removal of hormones and pheremones that carbon will not remove. Discus breeders rely on this method more than any other type. It is known as a semi-open system.

If you are breeding fish with the sole intent to sell them later then the growout tank must recieve a minimum 50% water change per day to maximize growth and health in the fish.

I do 100% water changes every Saturday on all mt FW systems. Thats about 4,000g per month in my fishroom.

 

[Potts050]

50% thats a lot!
It must depend on loading density and feeding rates as well.

 

[Mr.Firemouth]

When you have growout tanks, slight levels of ammonia and nitrite can occur because the fish are growing, the bio-load is changing, and it is best to feed often(up to 6x's per day). These slight elevations of levels can cause defects in the growth of the fish like

ammonia burn of the gill plates which will cause the edges of the gills to have erosion that will never heal.

Defective finnage like in Angelfish where the dorsal is bent

Stunting like with Discus where the eyes are too big in porportion to the fish because the body has stunted.

There are other things too but you get the idea.
The large daily water changes when growing out fry maximizes the growth and health potential of the fry in question no matter the species.

HTH, Rich

 

[Potts050]

When you have growout tanks, slight levels of ammonia and nitrite can occur because the fish are growing, the bio-load is changing, and it is best to feed often(up to 6x's per day). These slight elevations of levels can cause defects in the growth of the fish like

ammonia burn of the gill plates which will cause the edges of the gills to have erosion that will never heal.

Defective finnage like in Angelfish where the dorsal is bent

Stunting like with Discus where the eyes are too big in porportion to the fish because the body has stunted.

There are other things too but you get the idea.
The large daily water changes when growing out fry maximizes the growth and health potential of the fry in question no matter the species.

HTH, Rich

It sounds as though a semi open system as you describe is the route to go. If you have a 1400 gallon system and want a 50% water change then you need to flush 700 gallons in a 24 hour period ie 29.2 gal/hr or .5 gal/min. How do you maintain even water temp short of a direct contact gas fired water heater?

 

[wataugachicken]

It sounds as though a semi open system as you describe is the route to go. If you have a 1400 gallon system and want a 50% water change then you need to flush 700 gallons in a 24 hour period ie 29.2 gal/hr or .5 gal/min. How do you maintain even water temp short of a direct contact gas fired water heater?

heaters inside the tank(s) keep the temperature stable, and you can also add heaters at other points in the system.