Low tech mixed reef crashing

[BCubeReef]

Hello Everybody,

My tank is 2 and half year old and is a 32g biocube. I have a kessil 160WE, ATO, heater, circulation pump and hammers, Lepto, FrogSpwan, Acans, Toadstool. Some scarlet hermit crabs and some snails. The tank is clean minimal algae growth, I do water change every two weeks with RODI and RedSea Pro salt.
My tank sees lots of variation of parameters ( I never test for anything except salinity) but that has not affected any corals I have. Almost all of them are close to two year old in my tank and shown decent growth (trippling in size almost). The corals have seen lots of ups and downs while I moved from places but they always survived bounced back and started growing not losing a single head. Recently when everything is going smooth, I am doing regular water changes and maintaining salinity. My hammer and blasto are loosing heads quickly and lepto has some bleaching. Softies look fine, including other LPS (frog, Acans).
Now that things are not working out I am checking for Alk everyday (Hannah checker) and making sure that it reaches close to 11 (as RedSea salt is 11). My Alk was very low around 6 when I tested first time a moth ago and now it is 8.2 (incrementing about 0.1dKH per day). No change to the setup or salt or RODI.
My issue is I am not able to understand how my tank worked well without ATO and any testing and inconsistent water change for two years with no deaths.
My phosphates are very low and I feed reef energy weekly around 2ml. Corals retracted one fine day and getting worse. Please advice other than Alk could cause this. What could be possible causes other than low Alk?


Thank you

 

[Iván Olalla]

How are your nitrates? It seems that at first your WC schedule was able to keep up with your coral needs, but as they grew they consumed more that what you can replenish. If your nutrients levels are low i would use an alk off about 7/8 dkh and keep it steady.... LPS do consume alk at high rates and you need to keep them in check. Stability is key and with many swings your critters will suffer.

One easy and cheap way to keep steadier numbers is with kalk, but we need some more info about your water chemistry

 

[SliceGolfer]

I believe you are raising Alk too fast. Bleaching can mean rapid increase of Alk or lighting. Also, maybe consider a lower target for Alk. 11 is really high and the corals you have don’t necessitate such a high DKH. Even though RSCP May mix at 11DKH, you need to factor the volume of your water change against total tank volume. Hypothetical numbers here, but if your tank is 7DKH with 30 gallons, and you change 5 gallons with water that is 11DKH, you’ve only increased the overall DKH by a small percentage.

 

[BCubeReef]

How are your nitrates? It seems that at first your WC schedule was able to keep up with your coral needs, but as they grew they consumed more that what you can replenish. If your nutrients levels are low i would use an alk off about 7/8 dkh and keep it steady.... LPS do consume alk at high rates and you need to keep them in check. Stability is key and with many swings your critters will suffer.

One easy and cheap way to keep steadier numbers is with kalk, but we need some more info about your water chemistry

Thank you for the response. I checked my NO3 and NO2 both are undetectable on Red Sea Test Kit. I have no fish and no food is added so I dont expect it to rise. It could be too low though for that I have started feeding Red Sea Energy more frequently.
I believe in your theory in fact thats the only reason I could see.

 

[BCubeReef]

I believe you are raising Alk too fast. Bleaching can mean rapid increase of Alk or lighting. Also, maybe consider a lower target for Alk. 11 is really high and the corals you have don’t necessitate such a high DKH. Even though RSCP May mix at 11DKH, you need to factor the volume of your water change against total tank volume. Hypothetical numbers here, but if your tank is 7DKH with 30 gallons, and you change 5 gallons with water that is 11DKH, you’ve only increased the overall DKH by a small percentage.

Thank you for the response. Yes I do think now that I did little too aggressive change about 1dKH everyday for 4 days. I was confused about the target Alk level should be 11 or lower, thanks for your advice.

 

[BCubeReef]

Thank you for the response. Yes I do think now that I did little too aggressive change about 1dKH everyday for 4 days. I was confused about the target Alk level should be 11 or lower, thanks for your advice.

Oh and I am making a 0.1 dKH increments everyday now to get to 9. I hope thats not bad.