Need some advice


New member
I'm having issues.... My tank went largely untouched for 6 weeks. No water changes, no dosing. I just kept the ATO full and fed the fish. My reasoning for not touching the tank was due to home renovations. While maintaining my 40h job, I was coming home and putting in another 50 plus hours at home trying to get the basement done so the disruption to home life could be kept to a minimal.

So.. first of two questions.
Why did my calcium go up to 620ppm from aournd 440-460ppm. I triple checked the results with LFS and bought a new test kit from API. All three results coincided with each other. The Alk was around 7dkh and mag around 1380 with SG at 1.026 and PH averaging 7.9. My calcium doser ran out the first week, and the alk doser ran out around the 4th week.

Second question, I've struggled to successfully keep fish long term. Mostly chromis, damsels and cardinal fish. My water parameters have been stable but the PH has always been low. Could my low PH be part of the cause. Does low PH indicate low oxygen content in the water column? I have already vented my skimmer outside and put an air boot on my furnace. These both make a big difference. When the skimmer is off for any length of time, the PH drops to around 7.6 ish until it comes back on. I have a wife and 4 kids plus two dogs in the house. Being winter here, the house is sealed pretty well. My water flow is between 900-1100gph with three power heads that flow aprox. 22gph. The surface of the water is agitated well both in the display and sump.

I don't currently add kalk to my top off but could. I've been nervous to add it as I'm not sure what it would do to my calcium or alk levels. I'm looking for advice on this topic. Also if I do add kalk, do I need to add it through a reactor or can I just saturate the top off water in my 5gal jug?

My tank profile is this, 120g display with 125g basement sump with super reef octopus skimmer vented outside, GFO/Carbon reactor, two dosing pumps dosing alk (baked baking soda) and calcium carbonate, 140lbs live rock, 3 inch fine sand, refugium with light on opposite schedule. The tank is lightly stocked
with fish (cuz I can' keep them alive) and mixed corals, softies, LPS and some SPS

Sorry for rambling on


Premium Member
Calcium can't rise without a source. Tap water can have some calcium in it, and sometimes buckets of salt settle in bad ways, which can confuse the issue. Also, the amount dosed seems unclear to me. In any case, I wouldn't worry much about the calcium level. I'd just stop and dosing and let it drop on its own. For that reason, I'd wait on adding Kalk to the system. You can dose Kalk later via ATO if the pump is slow enough, preferably a peristaltic setup.

The pH, even at 7.6, is fine for fish. I'd consider disease issues or perhaps aggression. Corals are more likely to have problems with lower pH levels.


Team RC
I agree with Jon, but would add that you should continue to dose alkalinity at such a level to keep your alk at or above 7.5, otherwise your corals will have a hard time pulling calcium out of the water. Also, I would check to make sure my pumps were calibrated appropriately and that one, particularly your calcium chloride dosing pump, didn't get stuck on or something happen with the programming.

With regard to your pH issue -- low pH doesn't indicate low oxygen, but rather almost always an abundance of CO2. It may be because of high CO2 in the atmosphere in your house (and likely is), but another contributing factor can be inadequate aeration in the tank -- often because of flow. For a tank of your size, 1100 gallons per hour is not sufficient to maintain corals at optimal health. Although not precisely an accurate measure of flow, people typically look for at least 20x tank turnover per hour, with many preferring 30 or 40x if you are maintaining SPS. I'm not saying that this is a cause of low pH in your case, but it may be a contributing factor.


New member
So in answer to some of your questions,
I was dosing calcium chloride via 1.1ml doser. I was dosing 216ML per 24 hour period.
I am dosing baked baking soda via 1.1ml doser. I bake it for 2 hours at 350 degrees on a cookie sheet. Its dosed 31.2ML per 24 hour period. Each doser is running once per hour to help keep stable parameters.
I understand that calcium doesn't go up if its not added via salt or dosing, but what caused it get there? I checked the salt mix I use, its 440ppm. My doser hasn't run since January. During the six week lapse, the basement was renovated and there was ALOT of sheetrock dust spread throughout the house even though all efforts were made to keep that from happening. I know some of it made its way into the tank as the room that houses the sump had a good layer of dust throughout. The only two things that made it into the tank over that six week period was the dust and the baking soda.
I don't use tap water in the tank, only topped off with RODI
What is the best way to get an accurate number of gallons per hour flowing through the return pump besides taking the rating of the pump at face value? Concerning tank turnover, are you talking just the return pump of return pump and powerheads combined?
How do I get better gas exchange into the tank without getting rid of the family? The surface of the water is agitated both in the display tank and sump and the skimmer is pulling outside air already. Should I add an air pump with air stones to help as well?
I've been thinking more about the atmosphere the tank resides in and it hit me. We live in a cold climate with an older house. We have been going through the house in the last couple of years making improvements in weatherization. We have replaced all the drafty windows with high energy star windows as well as exterior doors too. On top of that, the fish tank filter room used to be open but is now closed in with the laundry room and furnace.
How does a person find out how much dissolved oxygen is available in the water column for fish and corals? thanks for your suggestions and help thus far


Premium Member
The flow for aeration includes both the powerheads and the return sump. You might need to measure the flow from the return pump to get an idea of the actual flow, but I don't think it's worth the effort. There are calculators that can compute head loss, and the manufacturer might provide a chart to convert head loss into a flow rate. I suspect that the tank has plenty of aeration. Only reducing the carbon dioxide content of the air would help much, and that'd take a scrubber or an air exchanger. Personally, I'd ignore the pH.

You can buy a dissolved oxygen test kit, but I'd guess the tank is at full saturation. Salifert makes one.

As far as why the calcium level rose, we might not be able to understand that at this point. I wouldn't worry about it, but would measure regularly, maybe once a week, for a while to see that it remains at an understandable level.


New member
So I purchased the oxygen kit from salifert. I got a result of 6 two times in a row. According to their instructions, marine tanks should test at a level of at least 7. What is a desirable oxygen level? And how do I raise it? Can to high of a level be bad?
Bertoni, you mentioned an air exchanger... What is that?
Would it be a fairly safe assumption at this point to think that this low oxygen level could be a reason why my fish keep dying off? Also maybe why the corals look blaw and grow slowy? Sorry for all the questions, it seems that the more I learn, the more questions I have.


Premium Member
6 ppm is a tad low, but I don't think it'd be a problem. I might work on getting better surface agitation, and cleaning and tuning the skimmer. Both steps can help aeration.

An air exchanger brings fresh air inside and does heat exchange with air it expels, so your heating or air-conditioning costs don't explode.