Aquaponic Gardening

A Community and Forum For Aquaponic Gardeners

I seem to have gotten to that time when my fish, those around 3 inches long, start to die for reasons I can't determine. Two this week. The pH is OK though a bit low (and I'm adding lime to raise it), the ammonia is zero and the nitrite is zero. I am transitioning the larger fish, around 6 inches, to the adult food though they don't seem real interested in it. My plan is to exchange out about 1/3 of the water today to see if that helps. Any other suggestions? 

Views: 1198

Reply to This

Replies to This Discussion

Tilapia, the adults about 3 months old. 

Thanks for sending this, by the way.

The first one you sent seems to imply that the fry are the most susceptible and that's not the experience I'm having. The fry are doing fine. I'll take a look at this one too. 

Also, follow up with TCLynx or Rupert, or anybody who has experience with chloromine. (I'm on well water with no chlorine or chloromine), but it's my understanding that chloromine won't/can't just off-gas after a couple of days unlike chlorine. I think people use sodium thiosulfate or some such thing, to get rid of chloromine...but check with them or someone else who has dealt with the issue and how it relates to fish...but my understanding is that there is quite a difference between the two (chlorine/chloromine)...

I found this:

And if I'm reading this correctly, you have serious zinc trouble. For soft water, the table indicates a MAX reading of 33 microliters per liter, which is .033 ml per liter. And an average reading should be no more than 7.5 mcl, or .0075 ml. Is it possible that your lab report was in microliters and not milliliters? Anyway, 5000 mcl (or 5 ml) is safe for drinking water, so no problem for us doesn't mean no problem for fish. Interesting data, I've never looked it up before.
And, it shows much higher allowable readings for higher pH, and for higher hardness. Logically then, zinc toxicity would be more acute at lower pH, and you just experienced a fish kill and low pH. Might be time to invest in an RO filter

Here's my problem. Our "local" water, which comes via aqueduct to the Keys, is very very high in pH. Like over 8. A friend who is doing AP says he's been using the drip from his air conditioning unit, which is essentially distilled water. I'm going to test it for pH and then, maybe, pump it into my fish tank, slowly replacing what I have. Yes, my zinc levels seem to be about 3 times what they consider OK. I wonder why, then, that they don't all die at once. And why the fry are doing so well and are so active. Thanks again for sending this even though it makes for anxious moments. I have only been doing AP for five months so I'm learning every day. 

This may be a good opportunity to cuddle up with a good book, (and a scalpel, surgical gloves and magnifying glass)...seriously...I'm not a big fish person, but I do know that most metal toxicity (copper, lead, zinc) will leave some tell-tale damage on the gill epithelium...might be time to do some digging (or cutting)...

I'm pretty sure you (that study) need to take into account water hardness and alkalinity, and not just pH (though the 3 are interconnected) higher pH usually means higher carbonate alkalinity, and it is this carbonate alkalinity and the subsequent complexing of metals such as copper, iron and in all likely-hood zinc as well (probably most metal cations that we'd run across) with these carbonates that will alleviate toxicity issues somewhat as "pH" (but more correctly carbonate alkalinity, or carbonate harness, called kH) rises. As the metals react, transition to tri-valent form, form various complexes and/or precipitates (like malachite, azurite in the case of copper)...they become less harmful or even harmless...I'm sure that study probably addressed this alkalinity issue (haven't read it yet), just that we here in AP-land seem to have gotten comfy equating high pH with high kH (and this is probably the case most of the time, but then there are those other times...)....

This is how it works in nature, but don't anyone count on hard tap water saving any fish from zinc toxicity in a recirculating AP setting...that would be silly...Like on par with Cleveland Browns winning the SuperBowl type of silly-hope...

I've been at it for 2 yrs, still learning as well, in fact I'm learning how much I thought I knew at 6 months in, but really didn't.

Your levels are more like 4 times the MAX level, and 17 times the average level according to that chart. The reason death isn't sudden, is because it's an accumulated thing. Like alcohol. A little is good for you, a lot is not, and an accumulation of way to much in too short a time can be lethal. I read of an accumulated toxin contained in a mushroom called a false morel. Many folks eat them and refuse to accept that they are toxic. However, the toxin accumulates in humans, and after years of eating false morels, a dinner (same as the many before it), causes death. The fry have not had time to accumulate a toxicity. Same reason why short-lived small ocean fish are mercury safe, and the fat old big boys are swimming thermometers.

Another point. Acid is cheap and easy, so don't stress about "local" water having high pH. Just fix it (I bet you would benefit from the hardness, too), and it's fine to supplement some rainwater from the cistern too, but I'd keep it down to 10% or less. The condenser drip is distilled water, sort of, but I would open the AC and see if you have copper or aluminum cooling fins. Again, the only thing worse than zinc is copper.

Right on Jon. It seems like the mechanism behind most metal toxicity in fish is this accumulation (depending on concentrations of course). It may take a while, a few months in or whatever for the damage to take it's toll and result in death. 

Michael, have you noticed any weird behavior in the fish prior (days before) to death? Like gasping at the surface for air...not hanging out at the bottom with the other fish? Anything indicative of metal toxicity?

Sigh. Can't win can I. I'm sure I have metal cooling fins. All AC units do. A friend, however, is using AC water regularly without problem. Maybe he will hit the wall too. 

Reply to Discussion


© 2024   Created by Sylvia Bernstein.   Powered by

Badges  |  Report an Issue  |  Terms of Service