Slowed coral growth in established tank

[PooseReefer]

I have a reef tank system that is about 6-7 years old. For the last few years ive had very consistent testing and dosing. I use BRS 2 part but was using kalkwasser up until a year ago. I use dosing pumps for 2part and have noticed needing less and less to maintain levels, and have noticed a slowdown in coral growth. There is some algae but have noticed coraline almost non existent as well.

Basically i have been turning down the time the dosing pumps are on from about 6min x 10 a day (60ml) on 1ml/min BRS pumps to only 2min x 10 a day and levels are staying consistent. This has been fairly linear. I did have a large(er) acro colony die off but there are plenty of LPS in tank that took up (and still do) the lions share of the coral.

I had great growth on everything up until about 9months ago... Shortly after switching to two part from kalkwasser is only change ive made really, anyone else have this issue? Only other change was switching to a digital salt meter which revealed my refractomitor was off. I took PPT on NaCL from 31PPm back up to 35 over the course of a month or so.

Ive heard of some success with replacing crushed coral substrate, as mine is quite old, but maybe it is time for a calcium reactor?

Any ideas appreciated

90G
Alk 10.0
CA 430
MG 1500
AquaIllumination Lighting
NO3 1PPM
P04 near zero

 

[Lasse]

Only other change was switching to a digital salt meter which revealed my refractomitor was off. I took PPT on NaCL from 31PPm back up to 35 over the course of a month or so.

When did you do that?

Sincerely Lasse

 

[Nano sapiens]

Two things stand out to me:

1. Proper kalkwasser administration typically maintains a 'reef normal' to slightly elevated pH. Without it, you may have dropped down a bit. Lower pH levels have been shown to slow down calcification. Can you measure your system's current pH (light and dark periods)?

2. Lowered salinity can also slow calcification. As Lasse stated, the time frame when this issue was rectified is important to determine if it could be a factor.

 

[PooseReefer]

Two things stand out to me:

1. Proper kalkwasser administration typically maintains a 'reef normal' to slightly elevated pH. Without it, you may have dropped down a bit. Lower pH levels have been shown to slow down calcification. Can you measure your system's current pH (light and dark periods)?

2. Lowered salinity can also slow calcification. As Lasse stated, the time frame when this issue was rectified is important to determine if it could be a factor.

I brought the Salinity up to 35PPT from about 31 over the last two months, but the slower coral growth started before that. I have a PH probe on my controller and the PH is around 8.0 but is a bit lower than the 8.2or3 i enjoyed with kalkwasser.

But again, for about 9months now ive been lowering my dosing pump time to keep alk and CA the same each week. If the time on was the same as when i first started 2part my levels would be off the charts. Ive cut down the dosing to only a 1/3 of the original amount that was needed to maintiain weekly numbers at the beginning.

No lighting, flow, sump, skimmer changes. Just an older system i suppose. I did add a razorwrasse that my LFS claimed would take care of vermitd snails, but has not paid off.

 

[dadnjesse]

I agree that when using the Kalk you had higher PH levels and that attributes to the growth difference.

 

[Lasse]

I brought the Salinity up to 35PPT from about 31 over the last two months, but the slower coral growth started before that.

I asked because I do not trust digital salt meters (if they are conductive probes) total - they need to be calibrated too. But it is obviously not the problem.

I had something like that last december and the reason in my case was that my Hanna PO4 checker give false readings. When I thought I was at 0.1 - in reality - I had 0.02. I dose some PO4 and now is good again.

Sincerely Lasse

 

[Jet915]

When I added 2 part, I also kept using Kalkwasser as well so maybe the drop in pH is it?

 

[SPSReeferMI]

This won’t solve your problem, but I too had a salinity problem with my digital meters - that’s two of them! I switched to this and I’m in love with the accuracy:

High Precision Hydrometer

Ensure that your equipment is reading correctly and your aquarium is at the right salinity with Tropic Marin's High Precision Hydrometer. Many tank inhabitants are sensitive even to minor changes of the water conditions. Unfortunately as we've all experienced, salinity reading equipment as...

www.bulkreefsupply.com

Since I adjusted my salinity back down to 35 PPT, my tank did increase alkalinity consumption by more than 50% (my tank was only 12 months old, so take that with a grain of salt!).

 

[Nano sapiens]

I have a small 12 year old system, and I've seen what you describe happen once at around the 6-7 year mark. Kalkwasser usage went from an 80% full-saturated Kalkwasser/20% RO mix to needing only a 40% Kw/60% RO mix in a week or so (I check alkalinity every 2-3 days so I caught the rapidly rising Alk level). No major changes to the system or environment (such as temperature/humidity effecting evaporation rates) that would account for such a drastic change happening so quickly. It took a few months before the Kalkwasser dosage returned close to the previous level, but I never did figure out what happened there...

 

[PooseReefer]

Just an update to this post. Had a single short spine pincushion for about 3 years just die on me. I honestly think it just ran out of coraline completely and starved. After not changing anything else I should be able to tell shortly just how much of the potential coraline was kept in check. I added some crushed coral to the sump as a poor mans calcium reactor as well and really dont want to go down that route if it can be avoided.

 

[ScottB]

Just an update to this post. Had a single short spine pincushion for about 3 years just die on me. I honestly think it just ran out of coraline completely and starved. After not changing anything else I should be able to tell shortly just how much of the potential coraline was kept in check. I added some crushed coral to the sump as a poor mans calcium reactor as well and really dont want to go down that route if it can be avoided.

Have you always run low nutrient? Is your fish livestocking levels similar to your "better days"?

It has been my experience -- across all the systems I touch -- that a heavy fish load makes corals grow faster. They are a constant source of ammonia that supplement coral growth IMO. Yeah, you gotta do a bit more export work to keep the algae manageable but it is worth it to me.

 

[Timfish]

In addition to @ScottB comment fish poop has high levels of carbonates and is an essential part of the carbon cycle in reef systems. Endoliths and biofilms are also messing with the dissolution of carbonate substrates so it seems reasonable to me you may have lost some of the buffering capacity of your substrate and replacing it may be helpful.

I don't know if you've read up much on the microbial processes in reefs but all the benthic organisms, corals, algae sponges, etc. are messing with and being messed by the microbial processes in reef systems. One thing you might try is running a diatom filter for a day to reduce the microbial load on your system to see if the problem is microbial in nature.

 

[PooseReefer]

Two things stand out to me:

1. Proper kalkwasser administration typically maintains a 'reef normal' to slightly elevated pH. Without it, you may have dropped down a bit. Lower pH levels have been shown to slow down calcification. Can you measure your system's current pH (light and dark periods)?

2. Lowered salinity can also slow calcification. As Lasse stated, the time frame when this issue was rectified is important to determine if it could be a factor.

Update and SOLUTION. So to recap I had "old tank syndrome" no growth, with established corals. I recalibrated my Ph probes and put a doser on saturated kalkwasser to keep Ph at 8.2 - 8.25. Initially it was sucking up large volumes of the kalk, but eventually slowed down to about a gallon per day, maybe half gallon. I then added one of those cheap BRS C02 scrubbers to my curve5 skimmer and the amount used per day dropped further.

Ive already started to notice Alk dropping and the need to up 2-part, CA still high but also dropping also. Im nowhere near the uptake I had a year or two ago, but coraline starting to take hold again and overall tank seems quite happy and headed in right direction.... Not out of woods of course but things had ABSOLUTELY improved. 100%. One of the best moves/results ive made on the tank without question.

Thanks Nano Sapiens and others who suggested similar.

 

[Rmckoy]

This won’t solve your problem, but I too had a salinity problem with my digital meters - that’s two of them! I switched to this and I’m in love with the accuracy:

High Precision Hydrometer

Ensure that your equipment is reading correctly and your aquarium is at the right salinity with Tropic Marin's High Precision Hydrometer. Many tank inhabitants are sensitive even to minor changes of the water conditions. Unfortunately as we've all experienced, salinity reading equipment as...

www.bulkreefsupply.com

Since I adjusted my salinity back down to 35 PPT, my tank did increase alkalinity consumption by more than 50% (my tank was only 12 months old, so take that with a grain of salt!).

Back in the day ( early 90’s they have swing arm hydrometers but they also had similar to these but can’t remember the manufacturer
I had one but was always told the floating hydrometers were not accurate
More a pain to read
Are the tropic Marin ones similar to the old days ?

 

[SPSReeferMI]

Back in the day ( early 90’s they have swing arm hydrometers but they also had similar to these but can’t remember the manufacturer
I had one but was always told the floating hydrometers were not accurate
More a pain to read
Are the tropic Marin ones similar to the old days ?

I would be interested in other’s experience, but I really like mine. I compare it to using a refractometer and the Hanna digital meter. I think this is more reliable and accurate. Since there is no concern for calibration, I think it’s less time with increased accuracy.

 

[Nano sapiens]

I would be interested in other’s experience, but I really like mine. I compare it to using a refractometer and the Hanna digital meter. I think this is more reliable and accurate. Since there is no concern for calibration, I think it’s less time with increased accuracy.

IME, a swing-arm is definitely quick and convenient. Like any measuring device, it periodically should be checked for accuracy.

I still use an ancient swing-arm that's 40 years old (bought for my first SW tank back in 1980). It reads SG 1.022 for an actual SG 1.026 (checked against LFS electronic and mechanical refractometers) and has read consistently like this for at least 15 years.

I take it into the LFS once a year just to have them confirm that the reading hasn't changed. I also rinse it with fresh water every time I use it and rinse it with vinegar a few times a year to remove any deposits.

 

[Dkmoo]

Update and SOLUTION. So to recap I had "old tank syndrome" no growth, with established corals. I recalibrated my Ph probes and put a doser on saturated kalkwasser to keep Ph at 8.2 - 8.25. Initially it was sucking up large volumes of the kalk, but eventually slowed down to about a gallon per day, maybe half gallon. I then added one of those cheap BRS C02 scrubbers to my curve5 skimmer and the amount used per day dropped further.

Ive already started to notice Alk dropping and the need to up 2-part, CA still high but also dropping also. Im nowhere near the uptake I had a year or two ago, but coraline starting to take hold again and overall tank seems quite happy and headed in right direction.... Not out of woods of course but things had ABSOLUTELY improved. 100%. One of the best moves/results ive made on the tank without question.

Thanks Nano Sapiens and others who suggested similar.

Great to hear your problem resolved. Ph is one of the most underrated but most important factors in coral health and growth. I've been preaching that ever since the BRSTV video that talked about it. Check it out of you haven't.

I too have noticed significant coral and coraline growth since started dosing soda ash instead of bicarbonate and installing co2 scrubber to keep my Ph stable at 8.3

 

[Rmckoy]

I would be interested in other’s experience, but I really like mine. I compare it to using a refractometer and the Hanna digital meter. I think this is more reliable and accurate. Since there is no concern for calibration, I think it’s less time with increased accuracy.

When testing salinity . Does it bob in the water and take awhile until able to read ?

 

[SPSReeferMI]

When testing salinity . Does it bob in the water and take awhile until able to read ?

It does take about 20 seconds to stop bobbing. I hit feed mode on my Apex, drop it in, wait 20 seconds... accurate reading.

To give an idea of accuracy, I can easily spot 1.0251 vs 1.0253.

 

[Rmckoy]

It does take about 20 seconds to stop bobbing. I hit feed mode on my Apex, drop it in, wait 20 seconds... accurate reading.

To give an idea of accuracy, I can easily spot 1.0251 vs 1.0253.

It’s possibly the same principal but a lot more accurate
Good to know ....