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Help with stn and rtn (short-term and rapid tissue necrosis)
Posted: Fri Feb 14, 2025 7:54 am
by zenrow_8
Hi all, I'm reaching out for some guidance as I'm having some issues with my tank.
I've had it running for about 3 years now, and it's been SPS-dominated.
The past 4 or 5 months, I've been experiencing STN (Slow Tissue Necrosis) that comes and goes.
It all started around 5 months ago when I had an Alk swing from 6.5 to 8.5 while dialing in a new dosing pump.
A week later, RTN (Rapid Tissue Necrosis) started on 2 corals, followed by STN on a few more.
After losing most of my SPS, I waited about 4-5 weeks for things to settle down before restocking.
I started doing 15-20% water changes every week and reduced feeding to every other day since my p04 was at 0.30.
However, STN has started again.
In a panic, I removed my bio-pellet reactor 2 days ago, thinking it might be making my water too sterile.
My setup consists of a 3x2x2 tank with LED Zetlight 360pro and 3x39w T5 lighting, which I plan to switch back to all T5's (6 or 8) depending on the cost.
I have 1 actinic, 1 purple plus, and 18k lighting.
My skimmer is the Skimz 161, and I use a Tunze controller with 2x 6055 and 1 6095.
My test results show Alk at 7.6, steady for the past 4 months, Cal at 450, Mag at 1240, Ph at 8.1, Nitrate at 0, and Po4 at 0.25 since removing the reactor (it was 0.10 before removal).
I use RODI with 0 TDS and 0.00 p04.
I'm also starting to get green algae on the sand bed, which I'm worried might be a sign of a cycle.
I've redirected flow to that area, and I'm planning to create a small fuge in the sump.
Was removing the bio-pellet reactor the right decision?
Re: Help with stn and rtn (short-term and rapid tissue necrosis)
Posted: Fri Feb 14, 2025 8:36 am
by Fable42
What's your go-to salt for water changes? I'm seeing some pretty wild phosphate swings here. Those can be just as deadly as the alk swings you mentioned earlier. And now, with the bio-pellet reactor gone, you might be losing some beneficial bacteria. I'd consider supplementing with vodka or vinegar to help keep things stable. But my main concern is getting your phosphate levels under control - I'd aim for around 0.10. Maybe look into using a small GFO or something similar. Without some kind of phosphate control, you're gonna see those levels bounce all over the place. And just like with alk swings, phosphate changes can be just as damaging. I'd rather see some nitrates in the 3-5 range, with lower overall phosphate levels. But the key here is stability - stripping the water too fast isn't doing you any favors.
Re: Help with stn and rtn (short-term and rapid tissue necrosis)
Posted: Fri Feb 14, 2025 10:08 am
by Fable42
I know I threw a lot at you, but I just wanted to drive home how crucial stability is. You see, phosphate swings can be just as deadly as those alk swings you experienced. I'd aim for a more manageable phosphate level, around 0.10, and complement that with some nitrate, say between 3 to 5. The key is finding that balance and maintaining it. I'm not a fan of stripping the water too quickly, as that can cause more harm than good. And yes, GFO can be a bit of a challenge, but once you get the hang of it, it's relatively easy to maintain stability with small changes every few weeks.
Re: Help with stn and rtn (short-term and rapid tissue necrosis)
Posted: Fri Feb 14, 2025 10:19 am
by lumin5
How old are those RO membranes of yours, and do you have any idea what your TDS is currently reading?
Re: Help with stn and rtn (short-term and rapid tissue necrosis)
Posted: Fri Feb 14, 2025 11:38 am
by zenrow_8
Thanks for the advice guys. I actually replaced all the RO filters about 4 weeks ago, they were about a year old before that. My TDS reading is 0 and phosphate level out of the filters is also 0.00. I'm using Red Sea salt, the blue bucket one. Just swapped out my old titanium heater for a new one from GHL, hoping that might help. Also getting a grounding probe to try that out. Not sure what to do about the PO4 swings though, I'm starting to think that big and often water changes might not be the solution.
Re: Help with stn and rtn (short-term and rapid tissue necrosis)
Posted: Fri Feb 14, 2025 1:14 pm
by Fable42
I've noticed that after big water changes, I sometimes see STN. I've found that 15% is about the limit for me. It's all about change, I think. When you add new water with no nutrients, but your tank has excess PO4, you're essentially bringing it down and altering the balance. Water changes can be helpful if it's a trace element imbalance, but if not, they might do more harm. I recall Sanjay's speech from a few years ago at MACNA, where he said that sometimes, doing nothing and waiting for things to stabilize can be just as effective, or even better, than making massive changes and reacting too quickly.
Re: Help with stn and rtn (short-term and rapid tissue necrosis)
Posted: Fri Feb 14, 2025 3:04 pm
by Fable42
That salt's not the issue, it's not spiking my Alk. But sometimes too much change causes more stress, including big water changes. Unless it's an imbalance or trace element issue, I'm not sure large changes do much at all except bring down nutrient levels in mathematical dilution. I recall Sanjay's speech at MACNA, he said we often overreact to STN and doing nothing is a viable alternative that works just as well.
Re: Help with stn and rtn (short-term and rapid tissue necrosis)
Posted: Fri Feb 14, 2025 3:22 pm
by Bronx97
Another thing to consider, unrelated to water parameters, is the possibility of metal pollution. You might want to double-check if there are any iron, copper, or brass parts that could be in contact with or near the water. I've heard of cases where this can cause issues, like a friend who had rust dripping into their tank from tangential fans at night, or another who had an iron bolt holding two tube holders together.
Re: Help with stn and rtn (short-term and rapid tissue necrosis)
Posted: Fri Feb 14, 2025 4:20 pm
by zenrow_8
You might be onto something, I've got a frag tank that I barely touch - it's just a 20% water change once a month. The setup's dead simple, cheap skimmer, some LED lights, a basic wave maker, that's it. But you know what, it's full of Acros and they're all thriving.
I hardly ever check the parameters, just the salinity, and I just top up with RODI water as needed. It's funny, I was thinking about my main tank and how I'm always messing with it, and then I look at this little frag tank and it's just cruising along.
You mentioned metal pollution, I've heard of it, that's why I swapped out the titanium heater. But I have no idea how to test for it. Can you tell me, is there a way to check for it? And what about voltage leaks, can I use a standard multimeter to check for those?
Re: Help with stn and rtn (short-term and rapid tissue necrosis)
Posted: Fri Feb 14, 2025 4:35 pm
by Flowix
zenrow_8 wrote: ↑Fri Feb 14, 2025 7:54 am
Hi all, I'm reaching out for some guidance as I'm having some issues with my tank.
I've had it running for about 3 years now, and it's been SPS-dominated.
The past 4 or 5 months, I've been experiencing STN (Slow Tissue Necrosis) that comes and goes.
It all started around 5 months ago when I had an Alk swing from 6.5 to 8.5 while dialing in a new dosing pump.
A week later, RTN (Rapid Tissue Necrosis) started on 2 corals, followed by STN on a few more.
After losing most of my SPS, I waited about 4-5 weeks for things to settle down before restocking.
I started doing 15-20% water changes every week and reduced feeding to every other day since my p04 was at 0.30.
However, STN has started again.
In a panic, I removed my bio-pellet reactor 2 days ago, thinking it might be making my water too sterile.
My setup consists of a 3x2x2 tank with LED Zetlight 360pro and 3x39w T5 lighting, which I plan to switch back to all T5's (6 or 8) depending on the cost.
I have 1 actinic, 1 purple plus, and 18k lighting.
My skimmer is the Skimz 161, and I use a Tunze controller with 2x 6055 and 1 6095.
My test results show Alk at 7.6, steady for the past 4 months, Cal at 450, Mag at 1240, Ph at 8.1, Nitrate at 0, and Po4 at 0.25 since removing the reactor (it was 0.10 before removal).
I use RODI with 0 TDS and 0.00 p04.
I'm also starting to get green algae on the sand bed, which I'm worried might be a sign of a cycle.
I've redirected flow to that area, and I'm planning to create a small fuge in the sump.
Was removing the bio-pellet reactor the right decision?
I've been in your shoes before, and I've learned the hard way that stabilizing parameters makes all the difference for my corals. I used to get asked about my parameters, and I'd be like, "huh?" Those were the dark ages, lol. I had LPS back then, but now I know better. Just take it easy, don't make any drastic changes, and focus on stability.