Tiny zoas

I have a general question on Zoanthids. I have four types of Zoanthids in my tank and they are all spreading though some are faster growers than others.

My question is, Why are they shrinking? When I bought them they were wide open and fairly large. Most of them are half the size of when I purchased them. They dont look closed up they just got smaller. I test my water frequently (once a week) and the only levels that fluctuate are the CA and Mg and that is due to semi consistant suplimental dosing. I feed once every 2 or 3 days if that counts.

am = 0
nitrite = 0
nitrate = 0 (Fuge)
phosphate = 0
alk 8 to 8.5 dkh
CA between 350 and 400
Mg 1300 to 1400
temp swings between 78 and 80 during the day (It used to gt to 86 until I added a big fan)

I have a 55 gallon tank and a 4 x 54 watt T5 setup above it. The bulbs are less than 10 months old. I have about 70 pounds on liverock, 40 pounds of powder fine livesand. I will try and get a pic after work today but that may be a while. I unfortunately dont have any before pictures.

 

Even thou T-5 bulbs tend to last a yr or so, I personaly like to change them out a little sooner than that. Old bulbs can be one of the problems. Another problem that comes to mind is stray voltage. Do you have a Ground Probe? Where are they located in your tank? Are the "higher" placed zoas growing faster than the lower ones? I dont see any issues with your para's.


Luna

 

My experience is that my zoas can change shape/size depending on lighting level and the amount of flow. Unless they are not opening up for days at a time I wouldn't worry about it just let them get adjusted.

For example with light they may not need as much surface area to gather light if the light is stronger. I've found it can take a few weeks at least for them to really stabilize as well.

 

I've had the zoas for between 2 months and 6 months. One type is right at the top and they are the smallest. I moved that plug down a bit lower in the tank but they aren't much larger than the ones that got left right at the top. Others are down halfway down the rock so probably 12 inches below the surface.
I guess I'll leave them be.

 

I'd say your dKH is way low (I run mine around 12 or 13).

Also, I've read that T5 bulbs should be changed every nine months or so. Did they start shrinking only recenctly (like after the lights passed the 9 month mark)?

I doubt lights really follow the 9 month rule to the second or anything... just a 'guideline'.

 

They have been small since they went in. I know dKH is low but I can't seem to keep it above 8.5 or 9. I guess I have to start adding supliments to my top off water.

 

And I did replace my dKH test kit because it used to not register above 7.

 

I keep my alkalinity in the 8-9 range. It's perfectly fine, lots of tanks run 7-9 dkh. Natural saltwater is about 7.
It could just be your tank is different enough in lots of different ways from where they came from so they are different. There is a lot of stuff we don't/can't test for, who knows.

 

NSW has an DKH between 8-12, depending on the region. I dont see your DKH/ALK being an issue. The only "issue" that I can see is your temp swings.

Luna

 

I don't have a ground probe. I've never felt a tingle but that sounds like a good suggestion.

As for my temp swings. Is 2 degrees a big swing? I suppose I could turn on my heater and keep is set at 79 or 80 so there is less of a swing.