High Alk Consumption with very few corals.

[HWDylan]

I have a fairly large tank in the 350-400 gallon range. I am struggling to get my water parameters in line. I have been struggling to keep corals alive for a bit now. The tank has been up and running since January and I am still seeing almost no coraline algae. I have never worked with a tank this large before so excuse me if this is a normal occurrence but I am dosing 230ml of Cal and Alk a day to keep my DKH at 7.4. The only corals I have right now are a frag of Green Birds Nest, a very small chalice frag, and a frag of zoas. I cant see how this tank could be consuming this much Alk. I realize that a larger tank volume will have me dosing more 2-part (hence why people opt for Cal Reactors) but this seems crazy. I have looked everywhere in the sump and I cannot see anywhere where precipitation is building up so I dont think that is happening. I have seen that in the past and it was usually on heaters and such.

Some more info:
Auto Water Changes (35gal a week)
Alk: 7.4ish
Cal 420ppm
Mg: 1430ppm
pH: 8.3
No3: 25ish
Po4: 0.03

Any ideas?

 

[Trailermann]

yes, anxious to see the answer.

 

[Silent]

Your tank is fairly new and usually the first year can be unstable. Check your new saltwater and make sure the alk and other parameters are at good levels from the start and if not dose them before adding to your tank. Or use a salt that is high in alk.

 

[John08007]

Coraline algae? Are the car and mg dropping also?

 

[HWDylan]

Your tank is fairly new and usually the first year can be unstable. Check your new saltwater and make sure the alk and other parameters are at good levels from the start and if not dose them before adding to your tank. Or use a salt that is high in alk.

I use Tropic Marin Pro Reef so the Alk is around 7.0 usually. The tank is on auto water changes too so it very slowly does the 35 gallons a week. There should be no significant swing based on new salt water.

I was wondering if just the tank being new could be this unstable. This is not my first tank, but it is certainly my first of this size and it is a bare bottom which I know is challenging for the first year or two. I am more or less wondering if I am crazy to think that dosing 230ml a day of alk and cal is unusual. It is totally possible that I am just not use to a tank of this size. I just dont know where all that alk and cal could be going.

Coraline algae? Are the car and mg dropping also?

Almost no coraline algae in the tank at this point. I dose Calcium in equal proportions to the Alk. I have not had to dose Mag yet. The water changes seem to keep up with it as of now.

 

[Silent]

If you go to brs and use the calculator and see how much alk you need to dose a 400g tank to raise it plus the extra 35g a week of new saltwater i bet thats a whole lot of alk. After you get it to the level you want you wont have to dose much, especially if you adjust the new saltwater before it goes into your tank.

 

[Will Wohlers]

That does seem odd to me as well. Is it precipitating anywhere when dosing? With that few corals and volume of water I would expect to barely see a change in alk between water changes

 

[HWDylan]

If you go to brs and use the calculator and see how much alk you need to dose a 400g tank to raise it plus the extra 35g a week of new saltwater i bet thats a whole lot of alk. After you get it to the level you want you wont have to dose much, especially if you adjust the new saltwater before it goes into your tank.

That's where the issue is. It's at where I want. 7.4 is ok by me but it keeps falling and I keep upping the dose. I thought it was stable at 170ml but then I checked like 3 days later and it was down to 6.7dkh.

So there is a consumption happening.

That does seem odd to me as well. Is it precipitating anywhere when dosing? With that few corals and volume of water I would expect to barely see a change in alk between water changes

I can't see any precipitation. Not on the heaters or on any where around the dosing lines.

 

[Silent]

From your consumption rate it appears you need 133ml a day of each but that seems high for your bioload. Puzzling.

 

[HWDylan]

From your consumption rate it appears you need 133ml a day of each but that seems high for your bioload. Puzzling.

Yes, it's quite frustrating. I keep dosing and the alk just stays the same or drops. There is just no way 240ml of 2 part are being consumed daily. That's a lot for a tank with essentially nothing in it but fish.

 

[Will Wohlers]

Check mg level. If it's low then I've experienced the same issue you're having. Also how long after dosing are you testing? It could take a while with that size system for the alk solution to be mixed into the tank completely.

 

[ReefingBliss]

Have a similar issue with a 50 gallon. I am going through 50ml a day. Seems high I only have softies and a few LPS.

 

[HWDylan]

Check mg level. If it's low then I've experienced the same issue you're having. Also how long after dosing are you testing? It could take a while with that size system for the alk solution to be mixed into the tank completely.

Just checked all parameters a few min ago:

Alk: 7.3
Cal: 400
Mg: 1560 (red sea tends to read high in my experience)
No3: 5
Po4: 0.01


Cal and alk are dosed constantly throughout the day via Neptune DOS. Testing is normally done around 8pm

I have decided to stop all dosing and see what happens. There is something out of wack here and maybe letting it settle itself for a few days while continuing to test will reveal some insight.

I do have some cyano but no other algae really at all. Even cheato just slowly withers away when I try to add it to the fuge. I can see no reason why corals should die in this set up. Lights are around 300ish PAR . It's a shallow tank so not a ton of change from the bottom to the top. I don't think I'm killing them with light. The fact that almost no coralline is growing (even after adding a bunch of scraping from my work tank) after 9 months is a sure sign something isn't right. In my past tanks coralline usually starts pretty quickly after the cycle is done and the parameters settle. I have never seen a tank just be unable to grow coral like this.

I'm kind of at a loss here. Anyone out there experience anything like this?

 

[Randy Holmes-Farley]

Have you calculated the daily dose in dKH per day? That's the easiest way to judge if it is high or not.

 

[HWDylan]

Have you calculated the daily dose in dKH per day? That's the easiest way to judge if it is high or not.

It's about 1dkh per day that I'm dosing for a tank this size. That seems high for a tank with no corals and no coralline algae. Am I incorrect?

 

[Randy Holmes-Farley]

It's about 1dkh per day that I'm dosing for a tank this size. That seems high for a tank with no corals and no coralline algae. Am I incorrect?

Well, maybe. It won't be zero. These are many process that consume calcium and alkalinity, including precipitation on warm objects like pumps and heaters, on sand and live rock, growth of other organisms with shells (snails, etc.).

I don't consider 1 dKH per day worth worrying much about unless you see actual problems in the tank, like a seized up pump, hardening sand, etc.

Even a soft coral tank can use 2 dKH per day without apparent issue.

 

[HWDylan]

Well, maybe. It won't be zero. These are many process that consume calcium and alkalinity, including precipitation on warm objects like pumps and heaters, on sand and live rock, growth of other organisms with shells (snails, etc.).

I don't consider 1 dKH per day worth worrying much about unless you see actual problems in the tank, like a seized up pump, hardening sand, etc.

Even a soft coral tank can use 2 dKH per day without apparent issue.

That is interesting. Glad to hear that is isn't as crazy as it seems. I cant imagine how this will be once I am fully stocked with LPS and SPS corals. I see a Cal Rx in my future for sure.

So then, you do not think this is related at all to my inability to keep corals (even zoas) alive in the tank? This is also an issue I have never had. I have several successful SPS tanks and have never had a problem keeping stuff alive. Ive never seen Alk consumption like this before so I just assumed the two were related but it is possible that it is some other issue. Should I start looking for contaminants in the water? My Triton test came back almost perfect.

Side note: This is a bare bottom tank so there is no sand bed at all and the tiny bit of coraline I do see shows up and fades and dies within the week.

 

[Brew12]

I have a few questions. Any idea where your pH is and how stable it is during the day?

Did you do anything to cure/soak/clean the rock prior to use?

Do you have a grayish coating on your rocks?

 

[HWDylan]

I have a few questions. Any idea where your pH is and how stable it is during the day?

Did you do anything to cure/soak/clean the rock prior to use?

Do you have a grayish coating on your rocks?

First off thank you for helping out.

pH is between 8.15 and 8.35 daily. I run my skimmer air through a CO2 scrubber so it stays pretty high.

I cured the rocks by soaking them in bleach. That is it. I bleached and then soaked in RODI with Prime for weeks. I changed the water several time with new RODI and Prime to make sure to eliminate any bleach still left over.

There does seem to be a thin bacterial-looking film on the bottom (ABS Plastic) and rocks. There was a time when it was worse but it has receded a lot in the last few months. Now I am getting Green Cyano (pictured) since I started dosing KNO3. No other algae of note.

 

[Brew12]

So no algae, no coraline, dosing nitrate despite no obvious nutrient export other than the skimmer and what could be excessively high but balanced Alk and Calc consumption?
And, on top of that, coral don't stay alive.

It definitely seems odd... let me do some digging.