When should I make my first water change??

Hey, I've been running a 125 gallon for close to a month now, and finally my levels have pretty much dropped to zero. I only have 2 adult clowns, and 5 green chromis in the tank, that's it. Ammonia, and nitrites are at 0, but nitrates are at 1-2, so I guess it's still needs to drop a bit. Weird thing is my Ph dropped from 8.1 to 7.7?? I just tested 10mins ago, but my last test was 3 days ago, I haven't done anything to the tank other than top offs with RODI water, don't know why my Ph dropped like that.

But anyways, I still do have diatoms in the tank and they aren't just "going away" like the LFS said they would yet. Any advice on this??? Or just wait it out?


But back to my original question with my parameters how they are, should I do a water change at all? Or just keep letting the tank do it's thing for another week or 2?

Thanks so much! If you need pics for whatever reason, I can add some of the tank.

 

If your N03 is 1-2ppm that's pretty darn good. Alot of ppl struggle to get it under 10.
Since your ammonia and nitrites are showing 0's you can start a regular water change regiment today. This will help bring your pH back up to 8. I like mine to stay as close to 8.4 as I can keep it w/o going over that or under 8. Since I don't know if you've tested alk I'm not gonna recommend anyway to bring pH up other than the waterchange.
The diatoms will die off when all of the silicates in your system are used up. Then every time you add any new plastics, ie pumps-pvc etc, you will see other smaller, shorter lasting blooms since plastic contains silicates.

Welcome to 3reef!

 

another thing with regard to algae blooms, ph swings, and detritus buildup; make sure you have enough flow in the tank and enough surface agitation.

my PH was dipping pretty low and then i read somewhere on here that surface agitation was needed so i pointed a K1 at the surface of the water and its not been an issue since. the ph swing is low margin now. it used to be higher with less surface agitation.

dunno if that'll help.

 

I did test for alkalinity. I think anyway, thats dKH, right? sorry I'm new.. The dKH was at 8 exactly.

Should I add a buffer? Or just do a water change and see how that goes??

Any thoughts appreciated!

 

Petey463
a DKH of 8 is OK ( typically recomended values are between 7 and 12 DKH )

the PH drop - typically PH is lowest after dark when any algaes in the tank are consuming oxygen and giving off carbon dioxide
PH is normally highest during the lights on period where the reverse happens and CO2 is used up and oxygen created

always test late afternoon when testing PH IMO

As mentioned above , 1 reason for a low PH reading during the day could be due to poor gas exchange at the water surface , if the surface is not being adequately moved its harder for oxygen and carbon dioxide to swap places
this can be worsened if the surface has an oily, white film on it, as this also prevents carbon dioxide escaping and oxygen coming in

so a picture focused on the surface of your tank or a description of what you have in place for water movement would be usefull

simple test to find out if carbon dioxide is the reason for low PH
Take a cup of tank water - and measure PH
then add an airstone in there and pump air into the glass for an hour
measure PH again

if the 2nd measurment is higher than the 1st - it means carbon dioxide is causing your PH to be low.

credit to Randy Holmes Farley for that test description

oh and diatoms - leave em, and they will go -

Steve