by SantaMonica » Mon Aug 27, 2012 12:43 am
You can't have too much flow, but a bigger screen is not alway better. Use the size guideline above. If it's too big, the screen won't have enough nutrients to grow thick, and will always be thin and brown.
A scrubber (algae) does remove most of the "bad" things in tap water (after all, algae does all the filtering in lakes and oceans), but it is not known yet if they are ALL removed. And what certainly is not known is if they are removed fast enough for you to put tap water right into your tank for top-offs (it's already assumed that you are not doing water changes anymore, so we are not talking about changing huge amounts of tap water at once; just small amounts via top off). Chlorine is definitely not removed by algae, but chlorine will, in tiny amounts, evaporate as the water is circulated in the system. Chloramines (chlorine + ammonia) do not evaporate, but fortunately they are broken apart by ascorbate and ascorbic acid, both of which are produced by algae. After the chloramines are broken apart, the chlorine evaporates and the ammonia is eaten by the algae. Again the question is if this is done fast enough.
Some people are experimenting with using tap water instead of RO or RODI, but there are few results yet. I myself have a test 10 gal FW nano that I top off with tap (unconditioned), and for over two years it's been doing great. I pour in about a 1/2 gallon of tap water at a time. I also put a few gallons of tap water into my reef sometimes, but not enough to call it "top off" all the time.
If you have live rock, or live sand, or any corals or inverts at all, your problem becomes copper. Copper can occur in city water or in wells. Yes a scrubber (i.e., algae) consumes copper, but the question is will the copper be removed fast enough so that no damage occurs. It really varies by how strong your scrubber is, so it would be an experiment for you. The best test would be to start with an new tank, and add corals or inverts one at a time (cheapest first).
If you do add tap water, do it the day before you clean your screen, so that you have the most algae possible