Good to hear the levels are in check for alk
but if you are going to use suppliments like this, you should have the proper test kits on hand to check them yourself prior to each addition. This will ensure you do not have a future precip problem. The levels being fine now does not truely mean it did not happen though.
tested by the LFS
is pointless. Once removed from the tank, the reading will be skewed if the sample is transported. I would try to determine if it's not your test kit that is the problem or the water movement before you try fixing it chemically. Remove two samples from the tank and only test one right away. Leave the other uncovered and test it 1 hour later and compare the results. If the older sample has a better ph
, you still have a gas exchange problem. Keep in mind that the surface area of the sump is usually smaller footprint than that of the main tank so you still sacrifice good O2
exchange by using a glass lid. The skimmer does not contribute too much on the whole.