wow, that is really low. There is part of the problem. Gotta get the alk up to around 3.75 Meq/L or so. Differing opinions on the exact number, but around 3.75 Meq/L is where ya want to be. 8.0 is not bad at all, it is fine. You just don't want it to start dipping more. To raise it is a matter of good water changes since your so close to 8.2, and I like b-ionic 2 part (alk and calcium) to maintain it. Buffers don't raise pH, it only protects it. You can raise your pH by doing a proper water change which will follow.
As far as your light...do you have a pendant or a canopy? Either way, a small fan blowing on the surface of your water will do just fine. Even on really hot summer days, I put my clip on fan and my water never gets above 82. Remember, you'll be using FRESH water for your top off, not salt water. Especially due to evaporation. This is why your alkalinity (buffer capacity) is so important, since most fesh water is acidic, and in the 7.2 or so pH range, though you SHOULD test even your top off water for pH so you know what you are dealing with. Do not top off evaporated water with salt water, use only fresh (unless you are TRYING to raise salinity.)
Here is a waterchange informational. Doing this will help raise pH:
Mixing the salt is easy, and I'll just let you know how I do it.
You will need:
-1 cheap powerhead...like a rio 800 or a smaller maxi jet
-1 cheap heater around 100-150 watt
-1 cheap air pump and stone (somewhat optional)
-1 refractometer if you can...(hydrometers should be outlawed)
-5 gal or more bucket for the mixing( you have a 90 gal tank, you may want to look for something in the 10 gal range), another bucket at 5 gal to make it easier to dump in the tank
-salt mix
-good source water-no tap water unless its been tested
-a notepad to track all of your tests
1. fill bucket of any size about half with the water, then add appropriate salt for that amount ( i fill my 5 gal about 3gal worth, then with the instant ocean, I add 1.5 cups of salt) while stirring very well. (Salinity at the rate IO gives you will be around 1.022, thats too low, but more later about that)
Only add the salt to the water, never add water to the salt.
2. Finish adding your water to the bucket, then add appropriate salt again while mixing. At the rate IO gives you (1/2 cup per gallon) your salinity wil be around 1.022. This is when I add about 1/2 cup more to the water in addition to what I've added, and in a 5 gal scenario, it comes out to 1.025, which is about where you want to be.
3. Add powerhead to circulate and airstone to oxygenate (airstone is optional, i like it though)
4. cover and let circulate for around 24 hrs. A couple hours before you will use the replacement water, add the heater. Test salinity after water gets to targeted temperature, which for most is around 80. But acceptable range is around 77-82 give or take, varying opinions from many people.
5. Test salinity. If this is good, I suggest testing this water for ph and alkalinity and calcium and magnesium. This way you know the shortcomings of the mix. DO NOT ADD ANYHING TO THE REPLACEMENT WATER TO ADJUST except salt. It may cause a preciptaion event, which i learned the hard way one day If salinity is too high or too low, either add a little more salt or just unsalted water to adjust. If you must do this, let sit for a little while longer and circulate. Test salinity again.
6. Ready for the change? What I do, is I dump half of the 5gal into another 5 gal bucket, just to make it easier to handle the weight while pouring in. So that's why I have 2. And if you ave purchased a 10 gal mixing bucket or bigger, you could siphon out the water into the 5 gal bucket. You could also use the powerhead (thanks knowse) to pump the water into your tank instead of dumping it in.
7. Drain appropriate amount of water from your tank. Replace with new water.
8. Wait a few hours or so, then test your tank water. Given what you may know is lacking in your replacement water, plus the test on your tank water after replacement, this will give you a good idea what is needed.
Now you can add your b-ionic alk and calcium if needed and any other additives to the tank. Best to wait though to add anythig about 24 hrs and test then. But always test tank water before you add anything, and anything you add, do it slowly. Better to adjust over time than to try and quick fix things.
Hope this helps and good luck!!!
