Hi there,
I have just set up my new tank and I used 100 L of RO water to mix with the "Tropical Marine" sea salt and I thought the ph should be well balanced at around 8.4 but it turned out to be 7.7, what's the problem? I only added a Live sand base in the tank and let it ran for a day before I do the ph test. All others nitrates, etc was undetectable.
Also, I have just added a few piece of Live Rock into the tank today and it contained some alga, should I add any additives so that the Alga or bacteria inside the live Rock will grow better?
currently there is a few very small clams inside the tank as well, I got them from a beach near-by.
thank you

用RO來泡製海水 PH 會比較低一點，而您又是新的缸子，所以要升高PH
可以加強光照，加速藻類生長，PH會慢慢爬上來的

我當初就是考慮這一點,所以就直接拿自來水泡,約三週,PH值在開燈時約8.3
關燈後約8.0
不過以自來水泡,風險不小!!

I use a 150 HQI for 7 hours a day, would it be too much?
total volume of water would be around 100 liter.
I got some live rock with alga on it.

New tank, do not worry. Get rid of the clams as they will not go through the cycling. What kind of sand you add and how many pounds of LR you add? I would say have the light on for 10 hours for now. BTW are you planning to add any spplemental lighting to your existing set up?? if you are, then have the actinic light on for 12 hours and the MH for 10 hours. Do you have any water movement device?? Water circulation is very important. OK?
Do not add any additive at this time and let the skimmer do its job at pulling out bad stuff. Test your water for ammonia, nitrite and nitrate after a week. It the reading for nitrite and ammonia is 0, then the tank is cycled and you can add the animals you want slowly. Once you have animals in the tank, you can start to add additives. I would recommend you to use ESV's Bionic. I know for a fact that they sell that in HK, OK?? HTH!

to andrew,
thanks for your advice, U have been very helpful to me! and most importantly, U do know the shops in HK!!
I have bought the live sand that U recommended to me perviously, 2 pack of them, the sand bed is about 1.5-2 inch thick.
for live rock, I added about 6.5 lb of them. I will be adding more to it, at least 10 lb more but I want to add slowly in order to avoid overloading the system.
current, I do not have any high-grade organism in the tank, only very minimal alga that attached to the LR and the bacteria in the sand bed only, and the only energy source to the system is the HQI.
then the problem is will the system be laking nutrients for the alga and the bacteria? as I know that for a proper ecosystem, I should have a higher grade animal like fish who can consume the food that I feed to it and the fish then produce waste/food to the lower grade organisms and sustain the food chain until the end when the ammonia is changed into non-toxic form of nitrogen for the alga.
concerning the test kids. the no3 and no2 in my tank are both undetectable at the moment. the tank has been running for a week.
thanks!

I have told you to add the live rock all at once. Each time you add new live rock into your system, you are risking of another cycling. The transport of live rock from the store to your home could cause some die off of the bacteria. I am not sure where you got the idea of overloading the system, I have never heard that before.
You have a 30 something gallon system. The live sand is 20lbs each so you have 40 lbs of sand. I would recommend you to buy all the live rock you need and another bag of sand to fully establish your system. After adding another bag of sand, you should have enough depth for sand bed filteration. Again, add all the live rock at once.
I guess you did not clean the live rock. Usually, when adding the live rock into one's system, a preliminary cleaning procedure should take place. That mean scrub off any algae, sponge, tunicate, etc...
Do not worry too much about this as the synthtic sea salt contains all the needed trace elements to support your bio-load at this time. Skimmer will pull out both the good and bad nutrients but this is necessary especially you are a new set up. The low pH could also be causing the lack of buffer material. Sand bed alone unless you have really deep sand bed should be accompany by sufficient amount of live rock. Mr. Snake, ADD THE LIVE ROCK ALL AT ONCE!!!!
If it is set up for a week and the nitrite and nitrate are undetectable, I say your tank is done cycling. Since you need more live rock, I would say add the rock first, wait for three days and test the water to see if you have any detectable nitrite and nitrate, OK?? After that, you can slowly add the animals and corals you desire. Good luck!