I have fed my Garter/Ribbon Goldfish for 13 years. Is Thiaminase a problem?

[DrKate]

They put some additive that contained some copper compound or something.

I'm pretty sure what you're talking about is copper sulfate. It's a *very* common anti-protozoal (e.g. kills "Ich") treatment for fish, available over the counter and commonly used in overcrowded/stressed situations to prevent disease in the fish. I have no personal knowledge of its effects on snakes, but I'm sure that's the compound you're thinking of.

AND...

My question about the frozen thawed aspect of thiaminase is - if my silversides didn't have it in them when they were alive, surely I don't see it spontaneously appearing when they are frozen and stored

You are exactly right. I'm sorry I wasn't clearer about that. Different species (and populations) of fish naturally contain different levels of thiaminase. Some fish contain enough to be a problem even when very fresh (e.g. live). When *any* fish is dead and stored for some time, whatever thiaminase is present has time to break down the thiamine in the tissue of that fish. (Poor storage, e.g. too high a temperature, is also an exacerbating factor.) The stored fish become deficient in thiamine and lead to nutritional deficiency in the predator.

So it's not that thiaminase spontaneously appears, or even becomes more potent, in stored fish. It just has more time to do its job. And the more thiaminase that's there to start with, the more thiamine will be broken down during storage. The fish we talk about as "safe" are the ones that have extremely low levels of (or maybe no?) thiaminase, so not much (or no) thiamine is lost during storage. There are other fish (like herring for marine mammals) that have low enough levels to be safe when fed fresh/live, but cause problems if stored a long time. And then there are those species - like goldfish apparently, given the range of personal experiences here - that just vary so widely we can't really trust them.

If we knew exactly what it was about diet/environment that caused a particular population to have high or low levels of thiaminase, then presumably we could just raise low-thiaminase feeder goldfish. But without doing biochemical testing on each batch I don't know that there's currently a way to be sure that any particular batch happens to be safe.

Whew! Sorry for the long-winded reply. There just seemed to be some lingering confusion that I thought I could help clear up...