Low alk and mag

[GHsaltie]

I'll give a rundown on my tank and some of it's history first, then I'll go into the the problems that I'm having.
Tank is a 40g with 20g sump
7 months old, cycled with live rock
Reef Octopus 110 ss protein skimmer
Jebao rw-8 and two return nozzles are the sources of flow
Filter sock, sand chaeto and 5lbs of live rock in fuge
No chemicals, dosing, reactors etc. are being used
I use Salifert test kit and IO reef crystals

Brief history
6/25 NH4 0, NO2 0, NO3, 5-10, PH 7.8, PO4 0.1, Alk 9.1, Ca 420, Mg 1170
I moved a month after these readings were taken, on Sept 11th I added a hammer and an acan, the acan has since grown two more heads but the hammer is not thriving, more on this later. I didn't test the tank again until October, I know stupid, but life got in the way with moving and other things.
10/28 NH4 0, NO2 0, NO3 25, PH 7.8, PO4 0.03, Alk 6.7, Ca 390, Mg 1078
11/12 I added an orange plate and a green toadstool, toadstool was about 4-5in when expanded at the LFS
11/16 Green nepthea and another hammer added
11/18 Duncan added
11/21 NH4 0, NO2 0, NO3 25, PH7.8, PO4 0.03, Alk 7.0, Ca 420, Mg 1050
I do 20% wc every or every other week, that week that I added all those corals I did one on the 13th and 18th.

Okay on to the problems! I'm having some issues with my two hammers and the toadstool and I am assuming it's because of the low Alk and mag, but I'm not certain. The first hammer was doing great until about a month ago I believe, now it barely expands. The second hammer is very similar, it was really full and expanded until about 6ish days ago. The toadstool is not happy, I've tried it in two different areas but I'm afraid to move it again in case it gets worse, not once has it opened up and it's starting to curl into itself. Yesterday I also noticed a white patch on it, so I'm having a really hard time determining if the toad is unhappy because of parameters or other factors such as position, which is possible. All other corals are super happy, only these three are having problems. There are only three fish in the tank right now, a clown pair and a black combtooth blenny. I tend to feed heavy, hence the nitrates, and I target feed the corals 2 or 3 times a week.
Toadstool, see the white patch?


This is the second hammer purchased, both looked like this previously.


Second and first hammers, this is how they look now.



I think I covered everything, I don't know if this is the right section to put it in, but I figured since I'm having parameters issues it's at least a start. Any help guys? I really want to make my corals healthy and happy again.

 

[teamlounge]

What kind of lights do you use? How often do you change water? You may need to start dosing.

When alk drops below 7 your tank will stop drinking calcium also...could be happening now. As your tank matures...cycles tend to change along with what you add. Do a substantial water change and test. If things are still off, try dosing slowly and test again the next day. Rinse repeat until you get to proper levels...be patient with this. Slow is always better. Cut down on your feedings...no need to overfeed. Does more harm than good. Good luck.

 

[GHsaltie]

Light is a Kessil a360w-e, 20% water change every week or every other. I haven't looked much into dosing yet, if that is the route I should take where would be a good place to start, dosing for alk or mag? I have been cutting down on feeding some, thankfully I haven't experienced too many issues yet with that, my hermit crabs and porcelain crabs are pretty good at cleaning everything up.

 

[Randy Holmes-Farley Verified Community Expert]

What is the salinity? I suspect either it is low, or the magnesium reading is in error and is higher than you think. It hasn't declined from what is in the salt mix, and Reef Crystals has more than you report.

 

[Randy Holmes-Farley Verified Community Expert]

The current alk of 7 dKH is fine and isn't hurting anything.

 

[dragon99]

Keep up with the weekly water changes. That will help keep the ALK, Ca, and Mg levels up.

 

[GHsaltie]

Salinity is actually 1.027 right now. Normally I keep it at 1.024-1.025 but I accidentally made the last batch of water too high. I'm going to do another wc tomorrow to help bring it down.
I didn't know that Alk was fine being low, haha and here I was paranoid that it wasn't going up. What about the PH? It's stayed consistently at 7.8 since I started the tank.

 

[Randy Holmes-Farley Verified Community Expert]

Salinity is actually 1.027 right now. Normally I keep it at 1.024-1.025 but I accidentally made the last batch of water too high. I'm going to do another wc tomorrow to help bring it down.
I didn't know that Alk was fine being low, haha and here I was paranoid that it wasn't going up. What about the PH? It's stayed consistently at 7.8 since I started the tank.

The magnesium is not likely low if that is the salinity. It may be testing error. Many folks have issues with magnesium tests, especially the Red Sea.

pH 7.8 is OK, but on the low side. I address pH issues here:

http://www.reefedition.com/ph-and-the-reef-aquarium/

 

[GHsaltie]

I retested Mg a few minutes ago paying extra attention this time and it came out at 1110. I do remember that when I did the tests last time I rushed the last couple ones, Mg included, because I was late leaving for work. So maybe the last reading was messed up and it has been getting a little higher. I also double checked my refractometer and it's calibrated and reading properly.

 

[Randy Holmes-Farley Verified Community Expert]

I retested Mg a few minutes ago paying extra attention this time and it came out at 1110. I do remember that when I did the tests last time I rushed the last couple ones, Mg included, because I was late leaving for work. So maybe the last reading was messed up and it has been getting a little higher. I also double checked my refractometer and it's calibrated and reading properly.

I just wouldn't bother measuring magnesium in this scenario. It will be exactly as came in with the salt mix.

 

[GHsaltie]

Okay, so you don't think my parameters are off or anything to worry about right now? What would cause the test to read wrong? Oh and one other question if I may, can salt go bad or become contaminated? I had a bucket of salt that I think got water or something in it when I moved because it became hard about a week after. I didn't think anything of it until two weeks ago, that's when I got a new salt and stopped using the old bucket. Could that possibly have caused any adverse effects?

 

[Randy Holmes-Farley Verified Community Expert]

Okay, so you don't think my parameters are off or anything to worry about right now? What would cause the test to read wrong? Oh and one other question if I may, can salt go bad or become contaminated? I had a bucket of salt that I think got water or something in it when I moved because it became hard about a week after. I didn't think anything of it until two weeks ago, that's when I got a new salt and stopped using the old bucket. Could that possibly have caused any adverse effects?

I do not know why the kit may be off, but many people have various issues with many kits, and magnesium does not deplete unless large amounts of alkalinity are being added without magnesium. You'll see lots of threads where folks use two or three different kits on the same water and get 2 or 3 very different answers. If they are lucky, one of them may be correct. With magnesium, I'd seen folks report a 200 ppm rise or drop in 24 h, which also is impossible.

Alkalinity is on the edge of my recommended levels (7-11 dKH), and boosting it a bit with baking soda is fine plan.

 

[GHsaltie]

I read the article from yesterday about baking soda and I think I'm going to give that a shot. I want to get it to 9 dKH and see how my tank does with that. I used the calculator in the thread and it looks like I need to use 6.4 grams or 1.4 tsp of baked baking soda, assuming 45g of water volume (I used another calculator to find that number). Is this correct? I'm also going through the sticky threads and reading those, I don't know which one is going to be more fried after this my eyes or my brain!

 

[Hans-Werner]

Do you run phosphate remover? Your phosphate concentration seems quite low while the nitrate concentration seems quite high. The low phosphate concentration and the imbalance may be the causes for the contraction of the corals. If you increase alkalinity now you may make it worse.

 

[GHsaltie]

No I don't run a phosphate remover. After the first 2-3 months of being set up the phosphate levels lowered on its own and have stayed low. Would you mind explaining a bit more why raising Alk at this time would make it worse? And also is it the low phosphates or the high nitrates that is causing the imbalance?

 

[Randy Holmes-Farley Verified Community Expert]

No I don't run a phosphate remover. After the first 2-3 months of being set up the phosphate levels lowered on its own and have stayed low. Would you mind explaining a bit more why raising Alk at this time would make it worse? And also is it the low phosphates or the high nitrates that is causing the imbalance?

When nutrients are very low, higher alk can lead to burnt tips of SPS corals, perhaps because the skeleton is growing faster than the tissue can adequately keep up.

If you stay below 8 dKH, you should be OK.

 

[GHsaltie]

Ok, so when you say nutrients are low, are you talking about phosphates in particular? I thought that it's better to keep them low. Ugh, chemistry was never my strongest class....

 

[Randy Holmes-Farley Verified Community Expert]

Ok, so when you say nutrients are low, are you talking about phosphates in particular? I thought that it's better to keep them low. Ugh, chemistry was never my strongest class....

No, either N or P. Either can be limiting to growth.

Many people target 0.25 to 5 ppm nitrate and about 0.01 to 0.02 ppm phosphate.

 

[GHsaltie]

Okay, so I need to work on getting the nitrates back down. When that's under control I can look towards slowly raising the Alk. So with the phosphates at 0.03, should I try using a phosphate remover or let it be? With my luck I'll try a remover and it's going to take ALL the phosphate out.

 

[Randy Holmes-Farley Verified Community Expert]

Okay, so I need to work on getting the nitrates back down. When that's under control I can look towards slowly raising the Alk. So with the phosphates at 0.03, should I try using a phosphate remover or let it be? With my luck I'll try a remover and it's going to take ALL the phosphate out.

I'd let it be.