Dosing and water change question

[ZapataInc]

So for those of you that dose. When you do a water change do you stop dosing for a little while? I get that dosing alk and cal helps keep these levels at a stable spot. But my thoughts are that when you do a water change that those levels will rise plus with continued dosing wouldnt that number stay at that new level?

 

[Tanster2]

I think that really depends on your goals, and whether you're someone that prefers high alk or not. I just keep my alk/calcium similar to the water that I mix. I'm using Instant ocean so I keep my calcium at 400ppm and DKH around 11. I only dose again a few days later.

Many people measure how much calcium their tank uses per day, and then replenish the exact amount via ATO or 2 part doser. So if I know my tank will use X amount of calcium a day, I'll just replenish it every other day when it drops. Using an auto dosing mechanism is the best way to keep those params steady, but it's not hard doing it manually either.

 

[jcook54]

I address this in 2 ways. First, the water changes I do are on the smaller side (5-10g) and I do them more frequently to keep thing a bit more stable. This typically equates to less than 10% of total water volume per change. Second, I have the auto doser set up to dose Calcium & Alk just under what the daily consumption is for my tanks. I manually dose to make up for any shortfall when I do my weekly (at least) testing.

For example, when I test my frag tank on a Saturday, if it's anything less than 7.5 dKh, I'll manually dose some Reef Builder. This way I can keep the Alk at my desird level of 8.0 dKh. Sometimes I'll test mid-week but usually it's only on the weekend. If I do a water change during the week with Reef Crystals, it might increase my Alk to 8.3 or 8.5 and I'd end up with an Alk of 8.0 when I test it again on Saturday. If it is, I won't dose anything. I personally like testing and dosing, it's almost therapeutic. My goal with auto dosing is to even things out, especially when I'm gone during the week. There are always going to be minor swings and my goal is to keep them as minor as possible.

 

[Rickdareefa]

I would say test your parameters then do the water change. Test again a lil while after the water change and see if it could be problematic. If you're only doing a 10% water change on a tank your size I don't forsee it making too much of a difference . If you keep it at about 8.5 dkh and 450 calcium you will have plenty of wiggle room without killing anything due to the momentary increase from the water change. Also you might wanna check the parameters of your freshly mixed saltwater. May not be as high as you think.

 

[ActiveAngel]

Great question! Everything you bring up is right on the money.

The 3 points I have to add are:
1) My dosing schedule is aimed at long term stability. So while Parameters will shift briefly in the short term. in the long term, they aren’t affected significantly by water changes.
2) I log water changes, water test results, and changes to my dosing pumps. This allows me to make manual edits to the dosing pumps as required whenever I see a trend in any direction.
3) If a person’s parameters are rising while dosing and doing water changes, maybe they don’t need to be dosing yet. If their Alk and Calc is seemingly replenished by water changes, dosing is unnecessary. This, or they just need to dose much less for their water change schedule.... until their corals grow a bit more.

 

[ichthyoid]

This really begs the question: are corals more sensitive to increases or decreases in alkalinity, or is their sensitivity about the same for either scenario?

My reason for asking: alkalinity tends to decrease steadily, but rises much faster with a typical (dump it & run) water change.
So a plot of alkalinity vs time for most systems, would appear as a saw tooth waveform, if you will. A slow steady decrease with a rapid increase.

In any event, I plan to set up continuous water changes, using balanced peristaltic pumps.
This along with an anoxic denitrator, which will supplement both calcium & alkalinity each cycle (3-4x's per day), should keep things pretty stable.

 

[dball711]

My dosing never changes, it’s based purely on consumption and that’s stable. Since the levels in my freshly mixed water match my tanks levels (about 98%) there is no need to mess with dosing. Dosing and water changes do not cause my levels to move, they contribute to stability and that’s the whole point. Spot in with ActiveAngel and ichthoyd’s comments.

 

[Dylan484]

+1 to using water that mixes up to what you keep your tank at is going to be the easiest and most stable method.

Dylan

 

[Adam]

Lot of good info here, and different points of view.

I also use a salt mix that has parameters is close to where I like to keep the tank. If water changes are causing a rise in any parameter it will happen slowly, even if the dosing schedule isn't modified, over the course of weeks and you'll be able to identify it to make and adjustment if you're doing regular testing.

Let's stay there's 100 gallons of total water volume and the Alk is kept at a steady 9dKH. You do 15% a week water changes and that change water is 10dKH. After the 4th water change the dKH would rise to 9.5. Looking at Cal the same way. System kept at 400 and change water is 450. After the 4th change it would be 424. The closer the salt mix is to the parameters you keep the tank at the smaller these changes will be. If you're seeing a bigger than usual swing then it would be time to test the next time you mix to see if there's a problem with the batch.

Another option would be to use a mix that is a slightly less than where you keep things and adjust it up manually at the time of the water change. But I try to use the KISS method whenever possible.

To come up with the numbers above I used the calculators at Hamzas Reef. Lot's of good ones there and I recommend bookmarking the site.

Aquarium Calculators

An index of useful aquarium calculators and converters.

www.hamzasreef.com

 

[Mom2Many]

In my last tank, that I dosed by hand daily, I skipped dosing the day of water change as I did a 25% water change on that tank on WC day. And that seemed to pull levels up enough on that day.

 

[tag]

I always approached it this way on my SPS tank. I want my Parameters as stable as possible. So I use a salt that mixed up is similar to my parameters. Red Sea Blue Bucket. Then I dose the new water to be exactly what my tank water is, then do my water change. That way, I never have to mess with my dosing pumps/amounts.