I do once a week changes, from my own RO system. I change around 30 litres that I mix with Tropic Marin salt. I do check it once mixed, and the average ph once mixed is around 8.

The lfs suggested that I might try a much bigger change, with water from them, which I did, changing about 70 litres at once, but that didnt make a difference either.

Just a quick update.. since the above post (2 hours ago) the ph has dropped from 7.92 to 7.86.

Could they be affecting the ph?

Hi Jen.. thanks very much.

The current readings are:
KH 11
NO2 0.02
NO3 10
NH3 0.07

I always thought that RO water was a ph of 7, so I learned something with this.. it is reading 6.8, but once mixed with TM salt, it goes to around 8.04.

I did tiny kalkwasser doses yesterday, all day, to get the ph from around 7.85 up to 8.1 last thing last night.

This morning it is down to 7.92. I know that it would naturally be lower in the morning, and will check it this afternoon, but am certain that it will have dropped further, if this trend remains true to form.

The substrate is AragAlive (sorry I ommitted that - my slip!)

I have something really strange going on and thought that maybe someone else may have experienced something similar.

I have a new Buyo TL 550 (138 liters). I filled it with RO mixed with Tropic Marin salt and got the salinity to 1025 and put in about 15kgs of live rock. I let it cycle for about 5 to 6 weeks. During this time, I regularly tested the water to see if I could notice the maturation spike, but during this time, all levels (NO3, NO2 and Ammonia) remained pretty much at zero.

My LFS said that sometimes tanks don't show the typical maturation 'spike' and that it should probably be alright to start stocking it really slowly.

At this 5 to 6 week stage, I put in 2 common clowns and a starfish. They all seemed happy and were feeding fine, although the male cf was not as interested in food as his mate. There was quite a bit of green hair algae on the tops of the rocks and it was suggested that this was quite normal for a new tank and that it would probably settle down within a few months.

After stocking, I noticed a slight increase in NO2 (about 0.02) and NO3 (about 2). All this time the PH had been around 8.2.

About a week into having stock in the tank, I noticed that the ph was starting to drop, so I used a teaspoon of TM Buffer, which brought it back up again.

I then noticed that the ph was constantly dropping and started using buffer on a weekly basis.

I then noticed that NO2 and NO3 and ammonia was fine, but the hardness was increasing significantly (it went up to about 16 at one point). The lfs shop suggested that I stop buffering, as this was causing the increase in kh, which I did.

When the ph dropped to 7.6, I got nervous and the lfs suggested that I try dosing with kalkwasser to get the ph back up again (without increasing the hardness). I was mixing a teaspoon of kalkwasser in about 340ml of ro water and when the solution cleared so that he unmixed kalkwasser was at the bottom of the bottle, I tried putting a tablespoon in at a time and the increase in ph was insignificant, so now dose about 200ml, to get an increase of about 0.15 at a time.

The hardness is coming down a bit (it is now on 11), but the ph just keeps dropping.

I was using a digital ph meter and thought that it may be faulty, so decided to get a Profilux 3 (I know - serious overkill, but intend to use it when I get a bigger tank). The ph probe has been calibrated with GHLs ph7 and ph9 reagents.

It was thought that I might have a lack of flow issue, so I got two controllable tunze nanostreams.

I also keep the lid open everyday until lights on time, so the lid stands open for at least 8 hours a day.

I introduced a cleaner shrimp about four weeks ago and he is happy. After about three weeks, the male clown was not looking happy and I took him into the lfs who put him in a quarantine tank and he sadly didn’t make it. They were sure that it was not tank related, so I replaced him about a week later and after about a week, the female started looking off (she seemed disinterested in food) and she died as well. It was thought that possibly the original two cf might have been from a bad shipment.

The water is clear and the algae has dropped significantly (since putting water in, we are about three months into the life of the tank).

I do a wc once a week with about 30lt of water. Last week, I did a big 50% change to see if I could sort out the ph. It was sitting at 8.1 after the change and within thee days, it had dropped back to around 7.86.

The tank is standard as sold (other than the Profilux and two tunzes - skimmer is the Buyo WG308, it has two bags of ceramic rings and a dozen or so bio-balls and it has a 1400 l/hr Buyo circulation pump.)

Has anyone else experienced anything like this? Can anyone shed any light on what might be causing it?

Sorry that this is such a long-winded post, but thought it better to give all the details, than possibly miss something that might be significant.