Do I need to keep my Alkalinity lower? Possible ULNS.

[Benjamin J. Young]

I've been reading that you should keep a lower alkalinity for ULN tanks. So I guess the better question is do I really have an ULNS and if so, how do I achieve a lower alkalinity?

To describe my setup, it's a 10 gallon tank. Shallow sand bed and 12lbs of rock. Plenty of flow and light with an Vortech MP10, a DC circulation pump, and a Kessil A360. I made sure the lighting PAR was adequate with a Seneye. The circulation pump pulls the water through a filter sock, then through a Ghost Skimmer (running full time), past the Neotherm heater (set at 80f, but Seneye reads 79.025f), and then back to the display. ATS is running too, and I have Kalkwasser ready to use in the ATS to keep the Alkalinity stable. I have Red Sea Coral Pro Salt, and I started the tank up at 35ppt salinity. I do a weekly 20% water change. I may start doing a 50% water change monthly. I cycled the tank, and did a 80% water change before adding the corals.

Here's the kicker: No fish (and no fish food). The only living creatures you can visibly see, is Acropora and Montipora. I feed them a small amount of Rotifers weekly. I have yet to implement Kalkwasser because I wanted to see how much Alkalinity was being used in the first week after adding corals before starting to dose it. I just read my Alkalinity after the first week, and it's reading 9dKH. At the start it was 12dKH (which seems odd to have that big of a difference). Nitrates are undetectable and phosphates are either very low or undetectable (I'm very bad with colors). The small amount of cyno I had actually mostly disappeared.

The corals so far look good, but I'm worried for the future after reading about ULNS and high alkalinity. Should I keep my Alk low and does that mean getting to a lower salinity slowly with water changes? I'm not worried about having a fast growing tank or anything, just having a stable and healthy SPS tank.

 

[Flippers4pups]

The term ULNS is loosly in reference to little or no N03 and P04. These systems work because they use amino acids and elements, plus coral feeding, with high nutrient export.

It sounds like you just have low to non detectable N03 and P04, with high alkalinity.

If your not intentionally trying to keep a ULNS system and are concerned about the high alkalinity and low N03/P04, take your skimmer off line during the day and on at night. Lower your light intensity till you get your nutrients up and possibly feed a little more.

N03 at 5-10 is ideal and P04 at trace of 0.02 is a good starting point with alkalinity being higher than 10dkh.

If all that doesn't help, dosing sodium nitrate and phosphate may be needed.

 

[Benjamin J. Young]

I forgot to mention I am dosing Amino Acids weekly too. I like the idea of a ULNS, as it seems like less maintenance.

 

[Flippers4pups]

I forgot to mention I am dosing Amino Acids weekly too. I like the idea of a ULNS, as it seems like less maintenance.

AA's are just a small part of ULNS. spot feeding corals is needed and is, sometimes, elements. It can be done.

Most of the guys that do ULNS are dosing and testing water, especially alkalinity almost daily. They feed heavy, corals and fish and have fairly aggressive nutrient export plan.

It's a lot of work in my opinion.

A friend of mine at a LFS was doing a zeo system ULNS full of SPS. Had just one spike in alkalinity and crashed his tank. He has since stopped ULNS and went back to traditional nutrient levels. Said it was like riding a razors edge.