Can alkalinity be this low or would I be having issues?

[bunchofsalt]

Tested water yesterday. I have just started testing calcium, mag, and alkalinity since all I have had is a couple soft corals but wanted to get things right where I could add a hard coral or two. Can this be right with my alk or would I be having visible issues in the tank?

90 Gallon Tank with 20 gallon sump

Temp 77
PH 8.1
Ammonia 0.0
Nitrite 0.0
Nitrate 20
Calcium 320
Magnesium 1200
KH 4.8
Alkalinity 1.71

I do a 10% water change weekly. And have Reefbreeders Photon 48 over the tank. Tank has been running since about March.

I know the calcium and mag are low as well...but have been getting good growth of coralline algae. See pic below -

http://i691.photobucket.com/albums/vv276/cardstokeep/1956%20topps/photo10_zps5db1ac0a.jpg

[lboud39]

Did you test it only one time? This has to be operator error if you have coralline algae growing.

[bunchofsalt]

I tested Sunday after doing a water change Saturday morning and then waited until last night and tested again with virtually same results (Wed night). I am using the Salifert KH/Alk test......

[downbeach]

Are you sure you're not reading from the meg/l column? That (4.8) would be near 13dKH.

[bunchofsalt]

I'm pretty sure I was reading it correctly...but I'll check again tonight. Has me puzzled. Sounds like if it were this low I would for sure have noticeable issues going on then?

I also don't like the fact my nitrates are so high...but haven't ever been able to get them lower then 20PPM

[bertoni]

The water changes might add enough alkalinity to keep some growth going. I'd get a second opinion, and work from there. Nitrate is safe at that level for most everything we keep in our tanks. Some stony corals might object, but that's not clear.

[bunchofsalt]

Thanks - I'm going to the LFS Saturday...think I might benefit from taking a water sample in and seeing what they get. Hopefully the alkalinity is fine and I'm just having to worry with getting my calcium and magnesium up some.

[bunchofsalt]

Well - I take the idiot of the day cake. I was reading the results backwards. Was reading the level of KH-Ind removed from the syringe instead of how much was left. The tip ended up right on the 3 mark, so I was figuring .70 instead of .30 So now my alkalinity looks more like 4.00 meg/L with KH value of 11.2dkh

Salinity is 1.0245 was my last number checked.....should I be close to 1.026 for hard corals?

[grant778]

Your Salinity is fine. 1.023-1.026 is the accepted range. I only keep a few stony corals, but I run my tank at 1.024 sg. The way I figure it is if something went wrong with my auto top off while I was away, and it failed to top off, I have two .001 units of sg to spare due to evaporation. You can certainly bump it up to 1.026 if you want, this would enable you to dissolve more calcium ions into your water, and depending on the salt mix you use, and the number and size of the stony corals you are keeping, you may not have to dose for anything.

[bertoni]

I would raise the SG to 1.0264 or so, but animals seem tolerant of a reasonably wide range of salinity levels.