What killed my Urchin?

NeonRabbit221B · Oct 24, 2019

I made a possible big mistake over the last few days trying to dial in dosing Alk and maintaining salinity. I have a 13.5 Fluval Evo with shrimp, corals, fish and my urchin. Tank has been pretty steady for about 6 months.
I was setting up my ATO for my reef-pi and accidentally knocked the sensor around which triggered my pump to kick on. This happened shortly after a 5% water change with a lower salinity to bring it down from a 1.027 to 1.026. I checked last night after the accidental trigger and it was 1.025 which I was previously running at. I got a call at work from my gf saying my urchin was "not looking so hot". She pulled it out and I went through my usual testing to see what caused it.

Here are my parameters
Ammonia: 0.2 (due to dead urchin)
Salinity: 1.025 (tested with two)
Nitrate: ~2
Phosphate: Difficult to tell with my tesk kit but its non zero and less than .2
Alkalinity: 9.5 (Significantly up from the 8.0 I got about 1 hour after dosing Alk)
Mag: 1470
Calcium: Roughly 500
pH: 8.2

Looking back at it I have not been feeding him Nori as frequently as I should have been (1/week type deal) and my tank it pretty clean with strong buildup of coralline (which I hear they eat). My intuition is that it was a salinity change that did him in but the alkalinity probably didn't help. Using manual Salfert test so my 8.0 could have actually been a 9 and I had some half bubble/drops that screwed my reading. Typically when I dose 1 mL my Alk goes up by roughly .5-1, not <1.5.

So what did the poor guy in? Poor feeding habits? Alkalinity swing? Salinity swing? Combo? Do I ditch all manual testing kits and spend my whole next paycheck on good test kits?

NeonRabbit221B · Oct 24, 2019

BTW everything in the tank looks okay. All coral polyps are looking good (except GSP cause sexy shrimp are doing their dance).

Jon Fishman · Oct 24, 2019

I lost an urchin.... I have 2 others, 1 the same kind as the lost one, and they continue to be fine...... sometimes I think stuff (not coral.... that is completely our faults) can just die..... and chasing a reason isn’t the way to go about it.

My tank has swung much more in salinity and temp during tank changes etc, so I wouldn’t look for a definitive answer, because then you will just be chasing numbers.....

My only concern would be if the detectable ammonia is truly from the urchin

NeonRabbit221B · Oct 24, 2019

Yeah it wasn't... GF def overfed this morning "cause they looked hungry" and I changed how I cut my frozen food.... She has been depressed and so I am trying not to show her any anger but this is the third time. Do you think Prime will help it settle or immediate WC? Doing a small 1.5 gal and making more RO water now.

I guess add one to my list of learning mistakes.

MERKEY · Oct 24, 2019

NeonRabbit221B said:
Yeah it wasn't... GF def overfed this morning "cause they looked hungry" and I changed how I cut my frozen food.... She has been depressed and so I am trying not to show her any anger but this is the third time. Do you think Prime will help it settle or immediate WC? Doing a small 1.5 gal and making more RO water now.

I guess add one to my list of learning mistakes.

I wouldn't add prime.

If the fish aren't breathing heavy and near the top.

Water change yes

NeonRabbit221B · Oct 24, 2019

MERKEY said:
I wouldn't add prime.

If the fish aren't breathing heavy and near the top.

Water change yes

Any reason why? I have before in emergency situations, would Zeolite help?

MERKEY · Oct 24, 2019

What kit are you using to get the ammonia reading?

NeonRabbit221B · Oct 24, 2019

Red Sea and checked again with API (barely showed non-zero).

Put the urchin in a cut of tank water and when I got home an hour+ later it was at a 2. I had an ammonia spike

Hermie · Oct 24, 2019

Probably starved. I say that because a salinity change of 1.027 to 1.025 will not kill a healthy urchin.
Where did you get it? How long did you have it?

NeonRabbit221B · Oct 24, 2019

NotASpammerDude said:
Probably starved. I say that because a salinity change of 1.027 to 1.025 will not kill a healthy urchin.
Where did you get it? How long did you have it?

Live aquaria and about 5 months or so once my nitrates/phosphates were under control. I am thinking I might have starved it. I only really have coraline algae and didn't feed it very often.