Backyard Aquaponics
A place to discuss aquaponics

When I started my system I was told that I'd to controlled the, temperature, the pH and the NO2 & NO rates.

I've just lost one trout when the pH = 6,8, NO2= 0 and NO3= 20… (temp around 7°C)
I've noted that it had light pink gills, full of mucus…

The day before the pH was 7,6

I'm wondering what happened.

I've read somewhere that it could come from ammoniaque (NH3) which may be created back under certain conditions.

Of course, i've changed 400 l of the water (30 % of tha total volume) and things seems allright.

What's your opinions/advices ?

Fish don't like sudden big jumps in pH. 30% is a lot to change.

you don't mention Ammonia

As a rule food fish are more sensitive to environment than goldfish etc.

but I am not a trout person - perhaps another may be able to give you a better reply.

A pH crash can occur with a loss of buffering capability in the system. Search for "Old Tank Syndrome" to see how folks in the aquarium business deal with this. Merck has a pretty nice high-level "manual" in their Pet Health Edition series about Fish Health, but nothing lept out at me in the Gill Disorders section: Disorders and Diseases of Fish.

Can you post some pics and more complete water quality test results?

How is the odor of the system? And the dead fish? Yeah, yeah... I know dead fish stink, but gill odors are particularly discriminatory when grading fish at the market. Probably not much of a clue it would provide here though.

--
Sam

At higher temps and pH's, ammonia will change into the more toxic form. What this means is that if you have ammonia and the pH or the temp goes up then it's possible that it becomes toxic enough to kill the fish. Ammonia should be added to your list of things you test.

+1 to what Sam (nosliwmas) said. At some point tanks can reach a stage where they don't have sufficient buffering to prevent rapid fluctuations in pH. If this is the case you'll need to add some buffering back into your system.

A pH change like this can also be caused by having large amounts of algae in your tank.

1) I have notice no special odor for water & fish

2) I have algae in the ST (mostly hairy green one) but not much

3) I enclosed a copy of the information i note every day.

Hope it will help you.

I don't know for certain how sensitive trout are to pH changes but usually it's better to do the adjustments on the top up water, not directly in the tank. You're shooting for a gradual change but only about 0.4 pH units per day.

It sounds like the fish is either sick or has had some exposure to a toxin. Increase the aeration of the water in the tank because the fish is having problems breathing. Since the gills are pink instead of brown it's probably not a nitrite problem even though you'd sometimes see deaths like this at intervals for quite some time after a nitrite problem. Look and see if you have any plants or materials that can drip or fall into the tank. An accumulation of these could be causing problems. Plant leaves in the tank and galvanized metal are two that I've heard of in the past.

Figuring out a disease is pretty tough without a microscope and some training but I'd take a look at this FAO document and see if anything rings a bell - ftp://ftp.fao.org/fi/cdrom/fao_training/FAO_Training/General/x6709e/x6709e15.htm

Posting a pic or two might be a good idea also

Thank you for this reply.

I add the salt into the FT and the acid in the filter (sort of radial one).

I have 2 air pumps blowing in the FT (about 820 l/h) + mechanical device (on return pipes FT & ST) to increase the air contact with water.

The trout is continuing to breath at the surface of the water; I have placed it in an other tank full of rain water.

If it dies (probably today), you'll have pictures.

Thanks for the document, i'm going to read it.