Up, **** pH, up!

[Kurt_Nelson]

Yes, I keep a close eye on salinity. 5g evap over a week out of 75g doesn't change the salinity that much (especially with all the ... salt creep that I seem to have),...

Actually... it does. If you start with 75g at 1.023 and let 5g evaporate without topping off, you end up with 70g at around 1.025. Over the course of a week, that's a fairly gradual shift and probably isn't a big deal to the fish.

... and replacement water is introduced with a air tube siphon and 5 gallons takes about 30 minutes to drain in, so even the replacement happens gradually to avoid massive swings.

30 minutes to go from 1.025 back down to 1.023 isn't really gradual. Granted, those types of swings might happen over say 60 minutes when you're acclimating a fish that you just brought home from the LFS, but that's a one time thing. Doing it at every water change is a little different.

Since you say you don't have corals, then it's probably not that big of a deal. But if you go down that road, don't expect them to take to kindly to those types of swings.

Regarding alkalinity, I'd consider anything between 8 and 12 dkH to be just fine. You keep saying your alkalinity is "so high", but I think it's right where you want it. I think your LFS is feeding you a little bad info - buffers will temporarily increase your pH, but it's just a quick fix. The main point of buffers is to increase the alkalinity. Here's a good link to understanding some of the many reasons your pH can be low...

Chemistry and the Aquarium

 

[Telek]

Thanks for the suggestions, some clarification on what I said:

Actually... it does. If you start with 75g at 1.023 and let 5g evaporate without topping off, you end up with 70g at around 1.025. Over the course of a week, that's a fairly gradual shift and probably isn't a big deal to the fish.

Yes, that is a very gradual shift, but I find that I also lose about 0.0005-0.001 based on my calculations (I assume at least partially to creep), so really it goes from 1.023 to 1.024 over about a week. Sometimes when I test I see 1.025, sometimes it's 1.023 after a week, it's never exactly the same, but those are the numbers I aim for.

30 minutes to go from 1.025 back down to 1.023 isn't really gradual.

It's actually over about 2 hours, and I aim to only bring it down by 0.001 after a change (0.0015 max depending how high it was). Draining in 5 gallons of water takes 30 minutes, but I'm not draining in pure water. Over about 2 hours (I don't swap the bottles immediately) I drain in 15 gallons. So the water goes down by about 0.001 in 120 minutes. Considering the overall daily fluctuations, and the fluctuations that happen in the wild I don't think that's out of line, but I am open to suggestion. If this really is too much I can start topping off in the middle of the week and doing the PWC on the weekend.

Regarding alkalinity, I'd consider anything between 8 and 12 dkH to be just fine. You keep saying your alkalinity is "so high", but I think it's right where you want it.

Well everything that I have found online states maximum range of 8-10dKH ( several said 6-8 ), so 14 is "so high", but if you guys are saying 12 is fine then I'm sure with a few more water changes using RO/DI and no dousing I should be back down to 12. Unfortunately my DIY saltwater is 13 right off the bat, so that doesn't help much.

Thanks again, I am definitely open to learning, but it just seems that there is so many differing opinions out there I don't really know what is "correct".

 

[Kurt_Nelson]

Definitely can't say you haven't thought it through!! Hey... if it's working fine, then I'd be the last to say change it.

To me, it just seems like you're making water changes a real hassle just to save yourself a few minutes (seconds?) each day putting a few quarts of water in. But as you mentioned, there's no real "correct" answer for many of these things!

 

[Telek]

Well honestly it's not much hassle. I figure that the water change should be done slowly anyway, and it's easy to put the water jug up on a shelf and let it trickle in. Since I need to test the salinity anyway it really doesn't take much to figure out how much salt to mix in the new batch. Besides since the salinity will go down on it's own anyway I can't just keep topping up with fresh water as then the overall salinity will decrease even more during the week.

 

[Kurt_Nelson]

Wow... you must have some nasty salt creep. Never heard of anyone losing enough salt to actually make an effect in their salinity.

Regarding speed of water changes... if you match your PWC water temp and salinity with your main tank, there really isn't a big deal. When I'm doing a water change, the actual time it takes me to pump my new water back in is about 2 minutes. Even with corals, I've never seen any issues.

 

[Telek]

Okie!

So after using RO/DI water for about 3 weeks (got myself a system installed) I'm down to about 7.5 dKH and pH between 7.75 and 7.9 depending on time of day.

So at this point should I be trying to get the KH and pH up at all? If so what is the best method for long-term change? I still have a bunch of seachem marine buffer left, but even with really slow water changes it caused fairly quick changes in overall pH (up 0.2pH in 30 minutes, then down again over about 8 hours) so without finding some way to easily throttle the input over a longer period of time I'm not sure that's such a great way to go.

Ideas?

Thanks guys!

 

[thincat]

Hi Telek, I assume that your tank is fairly new and the readings above is not out of line. I would just monitor it for now and let your system settle down.

 

[Telek]

Well it's been running for 4 months now, don't know if you consider that fairly new or not.

I have noticed since I switched to RO/DI and the dKH has gone down that the daily pH swings are much more now than they were with the high dKH (which makes sense)... So I'm just worried that going down to 7.75 at night is a little low since the fish supposedly like 8.1-8.4.

 

[thincat]

Check your PO3 and Nitrate levels. that might be part of your problem. Do you still have that glass cover on your tank? that could be another problem>