Meters can be rented from Hoskins Lab I think. A monitor that does 24/7 charting would be more useful than a meter because the data can be logged and one can go back to look at the levels from the logs when a fish dies unexpectedly at night. Those go for $2,000 though so not many people will own those.

Below is a chart of what I think is a typical a tank. The night bottom value might look low but that is probably typical for an aerated tank. I have no doubt that anyone running a skimmer in their system has enough DO. For those with tanks that are not aerated properly to begin with (using only powerheads or hang on back filters for example), the Idol could be fine for months but over time as algae grew or had a bloom, or the bioload increased, or there was lots of uneatened food one day causing decay and bacteria bloom, or summer came and the temp went up; then one night for whatever the reason, the DO drops just past the point needed for this particular fish and while it was fine for months, it unexpectedly dies (while everything else in the tank was ok). For tanks that have proper aeration (like a skimmer), DO wouldn't be an issue. The problem then is only turning it off and forgetting to turn it back on or turning off the return pump one night.

http://www.advancedaquarist.com/2006/10/review

http://www.advancedaquarist.com/2006...um/Figure3.JPG


If a tank has lots of algae, expect the range to be higher. Algae produces O2 during the day and consumes it at night. My results support this. When I had lots of algae, my DO range was large 50%-125%. When I had no algae, my DO range was small 80%-100%.

In this graph below (I think measurements from the Adriatic Sea), the spikes are due to algae growing near the sensor before they fixed it.

http://buoy.mbss.org/portal/index.ph...mid=58&lang=en

http://buoy.mbss.org/portal/images/s.../graf1_eng.png

The tank in question has constant flow and a large skimmer. Nothing changed between peak day and peak night, other than photosynthetic cycle. It is a very well stocked SPS tank, so I suspect that coral contribute to O2 consumption overnight

OK, I'll go with mysterious death, not DO related. :)

Just wondering how much photosynthesis plays in DO levels?

Forgot I was going to post a pic. Quick phone shot

http://i221.photobucket.com/albums/d...psjt9l6kgy.jpg

They look HUGE in there! Appear nice and fat in the pic though.

The pic does make them look bigger, but the big guy is a bit cramped. If he doesn't settle, he'll go to a bigger tank

Photosynthesis adds oxygen. With algae, I got plenty of supersaturation compared to having no algae. But my point was how algae can consume oxygen at night. In my system, it seemed to be significant. There are lots of articles on this topic.

Oh, the other chart didn't show up in my post. Here it shows what could be the oxygen levels of a typical reef tank throughout the day as measured by a $2,300 monitor from the other article. It varies wildly though depending on lots of factors. Some nights, the low will be lower and some days, the high will be higher. Shows the range from 3.5 mg/l to 8 mg/l

https://scontent-sea.xx.fbcdn.net/hp...ed&oe=559C23C1

Some things to consider for mysterious deaths :)

http://www.fishchannel.com/fish-heal...h-that-ph.aspx


Here is a case where someone was unable to keep flame angels after trying many including established ones. Looking at the list of equipment, I do not see an aerator like a skimmer. In my experience, I also had several healthy established angels (in separate incidents) die overnight when I turned off my skimmer (everything else was fine).

http://www.aquariumpros.ca/forums/sh...ad.php?t=30777

.

C'mon, you know what I mean. "Photosynthesis" as a cycle, so the respiration phase where organisms consume O2 :)

And who turns off skimmers, that's silly.

I didn't. I thought you were literally asking about photosynthesis which is specifically producing o2 as a result. So you really meant to ask what is the effect of cellular respiration (the opposite of photosynthesis). So as I said previously, in my tank when I had algae and no UV, my levels bottom at 50% (sometimes less) and now with no algae and UV, my levels bottom at 80%. I read in research papers that some reef fish like some gobies can survive in 3% saturation and damsels and cardinalfish around 10%-20% saturation. It goes without saying that different species will have different levels of tolerance to hypoxia. All of my mysterious deaths of established fish as I can recollect seems to occur when my skimmer was off overnight and always angels so far (pretty sure the MI would have perished too if it hadn't been relocated prior). Since the skimmer is in my DT, I turn it off when I do water changes, feed the fish, etc.

http://www.fondriest.com/environment...n-chlorophyll/

"Oxygen Depletion and Fish Kills
If an algal bloom appears, a fish kill can occur shortly thereafter due to the environmental stresses caused by the bloom. A fish kill, also known as a fish die-off is when a large concentration of fish die. The most common cause of this event is lack of oxygen 45."

I think (angel) fish dead overnight has some reasons other than oxygen. For a couple year, I ran a tank that has no skimmer. The tank had some very sensitive angelfish like golden and regal among other angelfish. All fish looked healthy and happy. As a matter of fact, one night I forgot to turn on my power heads after a maintenance. All fish were ok the next day morning.
I since upgraded that tank to a bigger one with a skimmer. But I am not hesitate to run a angelfish tank without a skimmer again. The only reason I wanted a skimmer in that tank was because I wanted to keep the water clean in order to keep some corals.

Honestly, even with O2 as a strong suspect, unless we monitor full time and chart values and find a sudden dip coinciding with a fish death, it's still mysterious dying fish syndrome.
The 2 in town that died. Tank is stable, nothing of any significance changes day to day, no power outages, etc. Fish survive fine for 6 nights, both die on 7th. What happened that could drop O2 to lethal levels on that night and not the others? Maybe something. Maybe not.

I did lose a MI and 2 large angels in a confirmed low flow setup overnight. I now have 2 MI doing well in a tank with surf conditions. But unless I spend a grand on an Apex DO meter and log O2 variances, we can't be sure what it or isn't happening.

In my case, it was reproducible. Flame angel a couple of times. Lemonpeel angel one time. Cherub another time. Always established for many months or years. Always after skimmer off overnight. Never a problem otherwise. If I had to guess, my DO level would have been around 20% (maybe much less. Eric's clownfish tank experiment had DO levels of 15%) without a skimmer running at night with a tank with algae.

Not saying this can be the only reason for mysterious death. But it is overlooked.

By the way, what was the reason for H2O2 dosing? To deal with an algae problem?

Not sure exactly. General cleaning, I think. I confirmed with the tank caretaker that it's dosed a couple hours after lights come on, so no evening impact.

Ok, so what I was trying to get at is if the dosing was due to an algae outbreak and whether the dosing had just started and algae started to die. Lots of algae, low ph, higher temp (my apt reached 30C last week), decaying matter all consume oxygen at night and was looking to see if the timing lined up with the deaths on the 7th day.

To be clear, I'm not saying people can't have skimmerless successful tanks with angels. Tanks can be aerated by means other than skimmers. That just means those skimmerless tanks didn't have hypoxic conditions. It doesn't mean other people's tanks don't have hypoxic conditions for some demanding fish on a bad day.

Anyhow, I know I'm beating a dead horse and have not been convincing enough. Maybe I'll have more to add when I get a chance to do some experiments on my own tank and intentionally lower my DO in a controlled way to see how my fish will react. Anyone know any biology students at UBC with access to a respirometer that want to do some research on reef fish hypoxia?

Ah. No, I'm told that there is about as little algae as you can get in that tank. The owner really doesn't like algae :) I think he has one little strand of bryopsis.

So back to the saga that is MIs. Today they started a bit of swatting at each other, so I may have to break the set soon. Not sure which one to keep, tough call. Big one is fatter, eats mysis better. Small one is still a bit skinny, but loves pellets and fits tank better. Also not keen to rehome one to hear it died a week later. In hindsight, ordering a spare might not have been #1 smart idea.

What do you feed more ? What's the more convenient fish for you ?

As you know, I gave up months ago on fish that needed specific feedings

I don't much care, I'll feed whatever the fish needs. I figure it's not so convenient for fish to be locked in my glass box, so whatever makes life easier for them gets done. On that note, anyone know the cost of oysters?? lol

Multiple MI aquariums is the answer

Yeah seems to me the issue is not enough idols :)

They're cheap, maybe I should get more??

Ah, this is now leading to MMITS - Multiple Moorish Idol Tank Syndrome


I'm telling you, this type of thing needs a vaccine

Vaccines kill, dontchaknow??

1 month anniversary, both fish doing well, getting along, eating almost everything. The thinner guy is filling in well, and fighting seems to have stopped. One eats pellets, not too fond of mysis, the other snarfs the mysis and doesn't touch pellets. Both eating nori and any fresh shellfish I add.

Overall, I'm starting to feel that these guys won't drop dead any moment.

:thumb:

Good stuff buddy. Are they getting along good? Is the myth of keeping them in pairs true or do they still fight?

Hard to say still. They have bouts of swatting, but nothing serious. But most people that complain of them fighting and eating things say it happens after a few months. I'll keep them paired as long as I can, hopefully they bond and live peacefully together.

Now that I think about it, I'm lucky with pairing. I have 2 pairs of talbots, a pair of clowns, a pair of cleaners and now these guys. The only fish not paired is a single talbots, which I'll try to find a potential mate for soon.

Oh, and a yellow tang. He's an ass.

Maybe they are he & she. :mrgreen:

Update: Both fish still doing well, although I had a bit of a scare. Alk hit 15dkh and that appeared to affect them. Breathing really hard and no appetite for about a week. I got the alk thing sorted out, and both are now doing well. Still getting along as a pair, always together and rarely swatting anymore. I had to turn the flow down, shattered a bulb 14" off the surface -lol

I'll get some pics as soon as I find my camera.

If anyone suggests that MIs don't eat SPS, they're lying :razz:

At least one of mine has developed a healthy appetite for polyps. Such food pigs, amazing how much they eat.

sounds like my version of a matted filefish. sorry to hear that after all the effort you put into this.

Oh no....that's not too good, is it sucking on the polyps or actually eating them? So...relocation?

They've stripped my sunset milli bare :) Not sure I can relocate it, it's well encrusted!!

I'm pretty sure he was talking relocating the MIs. He just wants yours too:lol:

Ya, I know :) No, fish are staying, it's only coral. I can grow more if I need to.

Ding it....lol

I have the just experienced a polyp eating idol as well. I purchased one from jl three week ago. I have always wanted one and felt I was up for the challenge he was eating pellets at jl I just couldn't resist.

When I first interduced him to to my tank he got picked on by my yellow tang for a good week and a half he got a nasty cut from the tangs spine I thought he was a goner for sure.

This last week he was accepted by the other tank mates and has made a full recovery. Unfortunately when I came home yesterday I noticed he was swimming around the tank like a boss I was so impressed for a minute and then I saw him going nuts all over my pink lemonade :eek:

I am definitely having second thoughts about him I knew the there was some risk but I was hoping he would eat some zoa ,digi or birdsnest and leave the acros alone.