[Fishfirst]

pH adjustment will be fruitless... it just won't work with a crushed coral base, but don't be worried, goldfish like a higher pH and the added buffering should keep the pH STABLE which is the most important thing. I would never do a major "cleaning" like that again, you damaged your biological filtration and now you are seeing new tank syndrome. Lightly feed, do water changes, and possibly get some biospira or stability in there. Filter size will not matter much unfortunately because you don't have the necessary bacteria to convert the ammonia to nitrate.