Turbo's Aquatics HF L4 scrubber

Just so there's no confusion, this is an Alk (Alkalinity) reading, so you don't need the alk test kit

 

Msg and cal are not taken up by algae, you need to maintain these levels with a regular dosing schedule. Alk can be taken up though, which might explain the. Low reading on that. Bottom line is that you need to keep these 3 in line on a regular basis. They are the main key to tank stability and longevity. With these levels fluctuating, or low, this can cause a variety if issues. This imbalance and irregularity can cause algae to get a foothold in the tank.

You can keep these more in line with regular water changes, or you can dose them. But if you rely only on dosing, then you can eventually end up with an ionic imbalance (depending in the product you use).

 

Do you have access to the dosing products for Alkalinity, Calcium, and Magnesium over there?

What about Kalkwasser? ...which incidentally is the same as Pickling Lime, so that should be easy to find - that will boost both Alk and Cal without throwing the ionic balance off. You can add this to top-off water

Then you can dissolve the lime in vinegar first before adding to the top off water and this will boost the Cal more while leaving the Alk alone. It's a bit complex but if this is a more available solution I can point you in the right direction.

Magnesium still plays a role. I find that in new tanks, it drops out faster than in established tanks (which can be tested every month, and boosted when it gets low)

 

Alkalinity (& potassium) is the only thing the scrubber could possibly be affecting. Your rocks & corals uptake alk (rocks sometimes a lot initially) and cal, and this will always be the case no matter what

There is no way PWCs should cost you less than dosing kalkwasser. Did you look into that? Pickling lime?

 

Yes, Alk and Potassium is really all you need to watch. Depending on your setup, Alk may not be affected by the scrubber, but if you are growing a lot of algae, it can.

Calcium Hydroxide is pickling lime. Are you sure you don't have that? It's the same thing you use to, well, pickle things. Far from dangerous.

http://www.walmart.com/ip/Mrs.-Wages-Pickling-Lime-16-oz-Pack-of-6/17339182

If not, can you provide a link to the lime that you do have available? It is important that it is the correct chemical.

 

Neither. It is a powder that is just pure calcium hydroxide.

It's super cheap

http://www.bulkreefsupply.com/brs-bulk-kalkwasser-calcium-hydroxide-aquarium-supplement-1.html

And you should be able to find it in a pure enough form in a grocery store. The link I shared to the Mrs Wages Pickling Lime is widely used in reef keeping in the US. The BRS version is likely better.

Kalkwasser is available from Brightwell Aquatics, Seachem, and dozens of other manufacturers but it's essentially all the same stuff: pure powdered calcium hydroxide

 

I assume you mean with both, not without?

 

You could run the scrubber even less than that if you wanted to, until the tank grows out and you have more bioload.

I understand what you're saying regarding nitrates. But you still want something present to reduce them, softies should do fine in very low nitrate water, as long as you are feeding there will be nitrate available.

The comparision between the large, new tank and the smaller, more established tanks is not exactly parallel because you have brand new rock in the tank, and as this rock cures, and as coralline starts to encrust, this will drop the alkalinity and calcium faster, so you're going to have to dose or do water changes to keep those levels in check, regardless of whether or not you are running a skimmer and/or scrubber.

Also the low alkalinity probably means that your pH is out of balance, probably low. Alkalinity helps support pH so you need this corrected and then you need to keep it there. Kalkwasser dosing really helps to keep the pH up. Once you figure out how much you need, you can mix it into your topoff water, or you can mix a saturate solution and dose a specific amount daily (or a couple times a day). But don't "chase" your pH by adding other things, just keep the Alk in check.

 

I think there are a couple things to consider.

One is that your bacteria is somewhat established, but there are still a lot of things happening biologically to establish the tank. Doing a very large PWC will "reset" the water levels to whatever the salt mix is, which varies widely from one brand of salt to another. So let's say your salt mixes at an alkalinity of 11, and your tank is at 7.7. That's a pretty big swing. Big swings can cause die-off, but with respect to bacteria, these will probably bounce back pretty quick. Without many corals in the tank, it's less of a concern.

Also your pH might be different between the tank and new saltwater. This could affect livestock. Then of course you want to match salinity and temp.

What I would do, if it's not too difficult, is catch the fish and bag them, and float in the tank while you do the PWC, then acclimate them after the PWC. This would reduce the chances of a death due to salinity, pH, etc differences with such a large PWC.

Might do the same with the corals, or just pull them to your frag tank for a few days then acclimate them back.

Also remember to let the salt mix for 24 hours or at least overnight before the PWC, then adjust the salinity as needed before you do the PWC. You can test the new SW mix if you want before you do the PWC but I wouldn't waste the test, just do a "baseline" test 24-48 hours after the PWC and then you will have your new "starting point". Then test Alk and Cal a week later and note the drop.

The other route you could go is 2 45% PWCs. Do one, wait a day, and test. It might be enough to reset the Alk and Cal to where you want it. But that all depends on your salt mix - which is why you might want to mix up 5 or 10 gallons to a salinity-matched level and test that water (after letting it mix for 24 hours).

If your salt mix has alk=13, then a 50% PWC with water that is at alk=7.7 would boost the tank water up to about 10ish