Can't keep up with Ca and alk demand in small frag tank

vessxpress1 · Nov 14, 2020

Hey everyone. My 20 gallon frag tank is struggling. The actual water volume is about 14 gal. The alk and Ca depletes so fast that I'm not able to keep up with it and I'm not sure what to do. I have a kalk reactor hooked up to the ATO and it almost seems like it doesn't help at all. I tested my alk this a.m. It was down to 6.8 dkH. I added my two part and bumped it back up to 9 dkH this morning and Ca was 441. Now lights are out this evening and I re-tested. Alk has dropped to 7.7 and Ca is now 426. ATO kicked in several times today and gave it kalk.
I have 5 small SPS frags and a larger branching SPS that I believe is a pocilipora and about a dozen quarter to half dollar sized LPS. Some of the SPS are bleaching. The LPS are all fine. This little bit of livestock drains the CA and alk this much?

I dose a capful of bionic two part every morning and it gets kalk in the top off and that's it. Apparently nowhere near enough now. I thought I would be fine with this set up but I probably should have stopped adding livestock of figured out a better dosing method. What should I do?

Fishfinder · Nov 14, 2020

How much evaporation do you have on that small tank. Kalk may not keep up. What test kits are you using?

vessxpress1 · Nov 14, 2020

Using Hanna checkers. I keep a top on the tank so that fish don't accidentally jump out during the night since it is shallow. The top off kicks in about 3 times a day. Maybe a couple times at night. I don't know the exact amount of evap it loses in a day but it isn't a lot. I should add it has a custom top with a screen in the middle and acrylic around the edge so it holds some heat in around the edges better, being in the basement. But it still evaporates through the screen in the middle.

Fishfinder · Nov 14, 2020

It would be helpful if you could try to find out. For example if you’re evaporating 1-2 cups a day that’s still under 1dkh of kalk being adding. Which isn’t a lot

vessxpress1 · Nov 15, 2020

It lost another 1 dkh during the night while lights were out. Is this normal?

HuduVudu · Nov 15, 2020

I have a 20 gallon mixed with a several large SPS colonies. What you are experiencing is normal for this size of tank. It is funny the smaller the tank the more difficult it is.

Your problem is two fold. Your water volume is small and your demand is high. That means that your tank will be very sensitive to any things that you dose. Any changes one way or another will move the tank fast. I purposely chose this configuration because it exposes weakness in my methods very very quickly.

Be warned at the water volume you are at dosing two part is going to throw your sodium and chloride balance off very very quickly. You absolutely need to be making largish water changes very regularly to keep this from getting out of hand if you are using two part.

The other issue that you are going to run into is PH. When you carbonate seawater you trade carbonate for hydroxl ions (base). This means you can not get your effluent from your CARX above 7 unless you add something for it.

I saw a guy that had a 29 high that he was running large SPS colonies in. I wish I had kept the link he is here on R2R. If I remember correctly he was running kalkwasser for his alk needs and then CaCl for his calcium and was doing I think 30% water changes weekly to deal with the chloride (Cl) imbalance. It might be worth the time to search for his build.

My way of mineralization is really experimental and I am still working out aspects of it, but I mostly have it down. If you are interested you can look at my signature block I have a link to what I am doing. I have some new things that I have started that I haven't added if you are interested I can post them out on that thread.

Hope this can help some.