2 fish deaths in 3 weeks

[MarkW19]

I don't have a sump; my substrate is ceramic media, not sand, but yes it is possible that the substrate is slightly stirred up during a waterchange (I add water slowly though). Is it possible to test for Hydrogen Sulfide in the tank?

Nothing new in the tank...

[thincat]

It is very difficult to test for hydrogen sulfide so the only way is to smell the water for a rotten egg smell.

[MarkW19]

Definitely no rotten egg smell. I'm due a waterchange in the next couple of days (new salt and re-calibrated TDS meter), so it looks like all I can do is keep my fingers crossed...

[thincat]

Yes, PWC can correct lots of problems. It will definitely bring down your nitrates.

[MarkW19]

Originally Posted by thincat

Yes, PWC can correct lots of problems. It will definitely bring down your nitrates.

Hi Thincat,

It's the PWCs that have caused all the problems - the last three of them have caused fish deaths - with no explanation so far! I'm trying to find out a reason for it, but no luck as yet.

When I said "fingers crossed", I meant I was hoping that the PWC goes okay without incident, and that my remaining fish are still alive after it!

[thincat]

If your PWC is the same temp. same SG and the same hardnest and the other basic elements there should be no problems. It's only fresh replacement water.

[Kurt_Nelson]

You'd think... but if you go back and reread Mark's posts, you'll find that's not the case. I'm still scratching my head on this one.

[MarkW19]

Guys, just had a major development with this.

I was due to do a PWC today; and as each of the last 3 waterchanges I've done have resulted in fish deaths, I decided to do a thorough test on the PWC water before I put it in (as opposed to the normal temp/pH/SG checks I usually do); yes I know I should have done this sooner, but this was the last thing I was expecting:

The new water has 1-2 nitrite in it, which I guess could be immediately toxic (death within 30mins-1hr) before it's mixed properly in the tank (approx 25% changed). I've tested this twice, and compared with a sample from my tank (0, ever so slightly pink as per test strip). Now, here's the strange thing: I've tested my RO water (made freshly yesterday, tested 001TDS) and the nitrite in this is completely clear (i.e. 0). No ammonia, by the way.

So, it looks like this is coming from the salt. This is Seachem ReefSalt. BUT, I used a brand new bag of salt for this as I was wondering if it was the salt that was the problem. I bought the two bags a month apart, from different sellers, so it'd be very coincidental that both bags have major problems and include nitrites; I've always used this salt without issue for the past 6 years.

I wonder if there's another explanation: bucket, powerhead, thermometer etc. I use that's got gunge built up inside it or something; could this cause nitrite to leech into the water? If not, is there anything else that could cause nitrite to develop, e.g. airborne or any other factors?

Hope to get to the bottom of this! I'm glad I've found this, as this was really questioning my interest in the hobby.

UPDATE: I've just tested a cup of RO water with a few spoonfuls of salt in it, and again this is showing 0. This wasn't even at the correct ratio/SG, or fully mixed (much more salt than normal, i.e. off the scale, just tested it out of interest). So, it looks like it's not the salt either.

I'm now going to mix just RO water (no salt) in my bucket as normal for the next 24 hours, and test it at different intervals to see how the nitrites change. I'll keep you updated...

[Kurt_Nelson]

Nitrites do not mean instant death for fish, so I don't think that's you're problem. HOWEVER... this is the first time I noticed you commenting about using test strips. I'd highly recommend getting some liquid test kits - not sure of available brands in the UK. I've found test strips good to use during cycling to just get a "rough check" of your levels, but if you're troubleshooting with them... that's not a good thing.

Sorry if you've already mentioned it, but are you using a refractometer to check your SG?

[MarkW19]

Hi Kurt,

I'm disappointed that the nitrites wouldn't be the problem, I thought I'd cracked it. Those levels of nitrites shouldn't be in my PWC water though, should they?

I'm not using test strips, I use liquid ones (Seachem usually, and I've also run a reference sample to check the accuracy. I've also had my LFS test my water before, and the results have been consistent with mine). When I said "test strip", I meant the results strip where you compare the colour of the water, with the strip.

Yes, refractometer. I try to do everything properly, where possible...

[Kurt_Nelson]

Originally Posted by MarkW19

Hi Kurt,

I'm disappointed that the nitrites wouldn't be the problem, I thought I'd cracked it. Those levels of nitrites shouldn't be in my PWC water though, should they?

Correct... you shouldn't be seeing ANY nitrites in the water, so something is wrong. While I'm no marine biologist, I don't think those levels of nitrites though are enough to be the instant killer that you've seen.

HOWEVER... with the test showing nitrites, I would start to suspect some kind of contamination of your water that could just be showing up on the nitrite test - but isn't actually nitrites.

I'm with you - I doubt it's your salt. It's not like Seachem is some no-name brand, and the fact that you've been using it for 6 years with no problems seems to point elsewhere.

Along the lines of what you said about the buckets, if it was me, I'd go buy new buckets and a new powerhead (or at least a different one) and start "fresh" with new equipment to rule out that possibility.

... When I said "test strip", I meant the results strip where you compare the colour of the water, with the strip.

OH... nevermind!

[mrg02d]

Maybe those nitrites are pointing to a dangerous nitrite compound?

What kind of plastic are you using for the water containment? Check your powerhead for rust. I know someone here awhile back had some deaths and found the stainless steel shaft in his powerhead had rusted really bad.

Matt

[thincat]

Look, It has long been thought that nitrites kill fish....Wrong, the latest research shows that nitrite only follows the break down of ammonia and it is the ammonia that kills fish. We thought that nitrite kills fish, but the real killer is ammonia. There can be no "nitrite" without ammonia. The fish died bacause of ammonia effects, not nitrite. We thought it was nitrite because by the time the fish died only the nitrite was showing up on our test...

[Kurt_Nelson]

Originally Posted by thincat

...
The fish died bacause of ammonia effects, not nitrite. We thought it was nitrite because by the time the fish died only the nitrite was showing up on our test...

Well then, I guess that clears that all up.

[mrg02d]

Originally Posted by thincat

Look, It has long been thought that nitrites kill fish....Wrong, the latest research shows that nitrite only follows the break down of ammonia and it is the ammonia that kills fish. We thought that nitrite kills fish, but the real killer is ammonia. There can be no "nitrite" without ammonia. The fish died bacause of ammonia effects, not nitrite. We thought it was nitrite because by the time the fish died only the nitrite was showing up on our test...

I wasnt suggesting nitrites formed from ammonia, but nitrites from something not commonly found in reef tanks. Its strange to have any nitrites in freshly made salt water. Seems to suggest some kind of contamination of the salt, or the water.

Matt

[thincat]

I stand by my statements.

[MarkW19]

Understood that nitrites aren't immediately fatal to fish, and that they have to come from ammonia.

But, in the case of my PWC water, this has shown 0 ammonia consistently, and obviously the bacteria required to convert ammonia into nitrite aren't in my bucket!

I'm with Kurt/mrg02d: I think contamination is a possibility, that's simply showing up as nitrite (but it isn't). I'm going to get a new powerhead/heater/food-safe bucket (had these food a few years now, although I always regularly/carefully clean them) to rule that out.

I'll report back...

[thincat]

You are on the right track. All I was saying is that nitrite is not your problem and that you have to look beyond that to find the source of your problem.