Max freqency of water changes.

[calhoun.22]

How often is it safe to do a water change in a 30 gallon system? Is it safe to do 5gal changes every couple of days to bring down nitrates to reduce algae?

29gal BioCube. I have no live stock yet. Tank has been up and running for about a month. Ammonia and Nitrites at zero. Nitrates holding steady at 10ppm. temp at 78 degrees. I have 2 Eshopps Sponges topped with a Poly Filter pad, SeaChem Purigen and SeaChem Matrix Bio Media in the fuge. I have a small skimmer on order.

I have been adding a little Purple Up, to encourage coralline growth. Also added some "Prime" in the beginning. I have about 25lbs of old rock that had been dry for a few years (previous tank) but seeded it with about 5lbs of cultured rock out of my LFS display.

The diatoms are going full blast, so I have not been running the lights. I just found some advice on another thread about how to siphon some of it off the rocks which I will do tonight. I am holding off on frequent water changes, just doing one a week. Can I do them more often to help bring down the Nitrates further or would I be causing another issue?

Also, is now maybe a good time for a CUC?

[bnumair]

generally 30% per month is a safe number. some like to do all 30% in 1 day (once a month) or some bi weekly (15% twice a month) some weekly or some like me daily 1%.
there is no set rule for how many changes. its all upto you what u can do comfortably. But small more frequent water changes are better.
Regarding algae. you need to do water changes and kill the lights. there is no livestock in the tank it wont hurt anything to shut lights off and make the tank dark by placing newspaper around it. this will kill the algae. do that for 1 week.
Nitrates of 10ppm is not harmful by the way.
Do not use purple up. its no use. its nothing but calcium and sand. if you were to check the parameters on Calcium, it will be off the charts.
no use for prime either as tank has no ammonia and nitrites.
diatoms will leave on their own after silica levels deplete in the tank.
yes you can do more water changes but for now i would do what i stated above along with 15-25% water change weekly along with trying to pull and siphon most algae out. then after you get the hold on situation go back to normal 30% per month water changes.

[calhoun.22]

Originally Posted by bnumair

generally 30% per month is a safe number. some like to do all 30% in 1 day (once a month) or some bi weekly (15% twice a month) some weekly or some like me daily 1%.
there is no set rule for how many changes. its all upto you what u can do comfortably. But small more frequent water changes are better.
Regarding algae. you need to do water changes and kill the lights. there is no livestock in the tank it wont hurt anything to shut lights off and make the tank dark by placing newspaper around it. this will kill the algae. do that for 1 week.
Nitrates of 10ppm is not harmful by the way.
Do not use purple up. its no use. its nothing but calcium and sand. if you were to check the parameters on Calcium, it will be off the charts.
no use for prime either as tank has no ammonia and nitrites.
diatoms will leave on their own after silica levels deplete in the tank.
yes you can do more water changes but for now i would do what i stated above along with 15-25% water change weekly along with trying to pull and siphon most algae out. then after you get the hold on situation go back to normal 30% per month water changes.

Awesome, thanks for the advice.

[Kyle918]

Welcome to Reef Central.

There really is no max to performing a water change. Generally though, you don't want to change more than 50% at a time. The reason for this is because you need to ensure the salinity, temp and pH match the water being changed. Changing 10% and having slight differences in temp for example shouldn't cause any adverse effects. But say you change 80% and there is a difference in temp, then that could shock the livestock. The more you change, the more you want to ensure your parameters of the new saltwater match that of what's being changed.

It seems like your cycle is complete since ammonia and nitrite are both zero. I would do a large water change, probably 50% to remove excessive nitrates. Nitrates of 10ppm are not harmful to marine fish. Invertebrates however are intolerant of high nitrates. Some coral are as well.

In regards to dosing, you should stop. You shouldn't dose anything to your tank unless you have a test kit to test the levels of what you are adding. How do you know if you are adding enough, in which case you're just wasting your time dosing inadequate amounts. You could also be dosing too much, thus wasting the product. Lastly, it may not even be needed, which I believe. Without a test kit for what it is you are dosing, you're just doing a process blindly and it probably isn't necessary.

I'm curious as to why you have diatoms as bad as you notated. What is your source of water? How long were your lights set for? Lights aren't needed during the cycle by the way.

Hope this helps!

[Stolireef]

Originally Posted by bnumair

But small more frequent water changes are better.

This is a pretty hotly contested point. If you want to 'move your numbers' with regard to nitrates as phosphates, larger water changes work better because of dilution. By way of example, let's say you want to cut your nitrates in half. A single 50% water change will do that (not recommending this but it makes the math easier). If you only do 25% water changes and want to get to the same result, you'd have the following result.
25% on first change
12.5% on the second change
6.25% on the third change
3.125% on the fourth change
etc....

So, on a 100 gallon tank, you have to change out over 100 gallons of water 25 gallons at a time over several water changes to get the same result as one 50 gallon change.

I opt for a middle ground doing 20% every other week.

[calhoun.22]

I'm curious as to why you have diatoms as bad as you notated. What is your source of water? How long were your lights set for? Lights aren't needed during the cycle by the way.

Hope this helps![/QUOTE]

Thanks for the comment and advice. I am currently using Distilled water in 1 gal jugs from wal-mart. I will be getting an RO/DI set up but for now this is what I am doing. At start up, a month ago I used water from our well. It is high in nitrate (20ppm) but all subsequent water changes have been with the bottled distilled water. I am using Instant Ocean Reef Crystals for my mix.

I think what got it (algae) started was that I was running my lights trying to get the coraline to grow. I have since stopped running the lights.

[Kyle918]

Excellent. Coralline algae will take a while to grow and it has to come from somewhere. If you started with all dry rock, then you will need to physically introduce some coralline algae to your tank in order for any to grow and spread.