Wild water parameters

Hey guys, I am fairly active on another reef forum but I thought I would come to the local guys to see if anyone has any advice for me.

This all started about a month ago when i changed my old and brown bag of purigen for a brand new bag and for whatever reason my pink Pocilliapora that had been growing like a weed, retraceted its polpys for 2 weeks then started to STN.  Thats when I knew things were funky. 

First a bit about my system.
Its a 12g nano-cube with about 10g of display water.

Filtration:
Floss, purigen, carbon, GFO, DIY Skimmer, and a maxi-jet 900 as the return pump

Vortech mp10 for the main water movement

I like to keep SPS but the problem is most of them die...

Here is what is thriving right now
Green Monti-cap

SPS that are not so happy and are STN'ing
Pink Pocillipora

SPS that seem to be unphsed (although I doubt they are)
ORA Verde Tort
Unknown Red Acro

LPS all seem happy
Candy Cane
Acans (3 different colors)
Hammer head

Some Zoas

Water Parameters
Cal: 410 (was 350 4 days ago and a water change)
Alk: I try to keep it above 7.5 but have to dose about .75dkh/day (and all done at night before bed)
Mag: 1380 (was 1280 before water change)
P04: .00-.12 (Hanna Checker and I always seem to get crazy numbers (I have red and green bubble algea as well as some GHA)

This is where it gets kinda crazy:
I siphoned a section of my sandbed and my Nitrates rose to like 80+ppm.  (I have pictures on another forum I can link if you want)


Any ideas on what I might want to do at this point?

I have a nano also (28 gallons, <20 actual gallons of water when factoring live rock) and always "had" issues when I swapping/recharging chemical filtration, e.g. carbon, GFO, etc. Honestly, I find that there is just not enough water volume to dilute the subtle effects of even minor changes. I'm loaded with SPS (acros, mili, montis, etc)...so I really have to be careful. The bottom line is I got rid of all my non-biological filters, including filter floss and synthetic sponge to limit big changes in chemistry.  

Here's what works for me and continues to work: 
1) I have rock solid stability using 100% natural filtration, which is from growing Chaeto in my rear reservoir/overflow and from have loose spacing of my live rock with deliberate low flow, mid flow, high flow zones.
2) I use very fine aragonite sand (3-5 inches...shallow in front and deep in the back) and a sand-sifting starfish. My sand has "almost" never been vacuumed/siphoned and is virtually detris free. This is from the starfish, my cleaner shrimp, and powerhead flow that sweeps the sand. 

There are many ways and mine is certainly not the best. I just find it works for me, and requires very little maintenance as I don't have much to do other than trimming Chaeto, water changes, and some calcium/alkh additives.  

Lastly, I struggle to maintain calcium/alkh (dkh) levels due to the low water volume and heavy sps needs. Kalkwasser top-off is a must for me.

Questions: 
What kind of lighting are you using?
How are you maintaining your calcium/dkH? 
How big are your water changes and how often? 
Are you feeding your corals, e.g. phyto and zoo plankton?

Thanks man,

for my lighting I'm using steves leds retrofit. 14 x 3w luxeon leds.

I try to dose nightly for alk with seachem reef fusion 1&2 and in the morning I dose for the calcium. I think the problem is I am not dosing enough to keep the alk or calcium up and when it falls I can't recover without massive dosing amounts.

water changes are weekly +/- 1 day of 1 gallon (about 10%)

corals are fed with 1ml of oyster feast or roti feast almost every other day.

I suspect the problem is that it drops so fast with manual dosing that it just doesn't have a chance to ever stabilize.

The key to SPS is consistency.  If you are only dosing your alk at night in a small tank the swings will be too great for the corals to most likely handle.  You would be better off using kalk or dosing two part all day with a dosing pump.

Would adding Kalk to the top off water be a good idea?  I am working on a dosing pump now with an arduino.

But looking into kalk, it seems like a "one and done" solution

I dose Kalk via a reactor, not through my actual top off, but it can be done.

Yeah I am hesitant to add anything to my top off water because I am afraid that it will fail on me. 

looks like I really need to automate some things sooner than later.

Also, what do you guys think about my water change schedule?  Is 10% a week enough or should I bump it to about 20%?

I used to do 10% per week, now I'm doing roughly 15% every two weeks. I made the change as I'm finding that dosing Kalk and - when needed - adding calcium chloride and sodium bicarbonate is keeping things up. 

This all said - I really can't say for sure why you are having these problems. All I can do is list the problems I've had and how I solved them...as a fellow nano keeper. The main issue, which I have addressed, is maintaining calcium and dkh levels. 

Other issues:

Nutrient Load: Since I'm keeping SPS, I added a nano-skimmer. It is working great and I don't think I could have the same level of success without it.

Waterflow:  Having enough turbulence has always been an issue for any tank I've kept. Even now, I believe I could use more...and still planning to get an MP10 at some point. You have an MP10...which means you probably already have more than enough water flow. 

Good luck

So I did a 20% water change last night and within 30 minutes everything was looking really happy!  Then the lights went out so we will see what it looks like when I get home from work today. 

I am thinking that once my levels dropped below a certain point I was just not able to keep up with the consumption without adding a MASSIVE amount of chemical.  Now that things are back in range, I will try to maintain them.

Alk: 8.4
Ca: 425
Mag: 1380

I don't want my alkalinity to drop below 8 and my calcium to drop below 420... those are my goals

Just an update for those that helped out with advice.

Basically I was not dosing enough/too infrequently and was bouncing off the bottom of the DKH scale that my tank could support. Once I went from dosing 1/day to 2x/day (AM&PM) things are starting to level out and be happy again.

I have received a dosing pump so that is going to make my life A LOT easier.

Anyways, thanks for the help!

How much are you dosing? I have a 15g cube at work that has SPS, LPS, soft corals, & maxima clam. I never have dosed my tank but I do weekly water changes and am using Red Sea Coral Pro Salt.

Hmmm....

I am dosing 1.2ml seachem Reef Fusion 1&2. Once in the morning before work, and once at night before bed.

Every night my Alkalinity is at 150ppm (before dosing) with hanna checker.