Contrary to some manufacturers’ claims, all carbons contain and leach phosphate. Phosphate in carbon does not arise from phosphoric acid washing of carbon, but from the organic material used to manufacture the carbon. Acid washed carbons are washed with sulfuric or hydrochloric acid, not phosphoric acid. Usually, carbons most suited for water filtration (macroporous) leach the most phosphate. Carbons designed for gas filtration (microporous) leach the least. A few macroporous carbons available leach relatively less because they have been pre-washed or acid washed to remove soluble components.

Red Slime

This one is simple. Do not use red slime killing products, usually erythromycin. Aside from jeopardizing nitrification and denitrification, antibiotics just kill off all susceptible strains of algae or bacteria, then a few weeks later the resistant survivors take over. Your slime killer stops working. The safest way to suppress red slime is with light, specifically with the long UV available in actinic sources. Increase the actinic light or other UV source and remove any glass or thick acrylic between the light and the water. UV sterilizers do not help with this because they do not illuminate the aquarium.

“Berlin System”

Finally, something else that keeps coming up. The new philosophy is that if the nitrate concentration is too high, it is because you have a too efficient nitrification filter. The solution is to dismantle the wet-dry or other filter and start relying solely on reef rock to do the job. Somehow, if you use reef rock as your sole biological filter you will have a balance between nitrification and denitrification.

Somehow, all that ammonia that is now being converted to nitrate will be processed in some other mysterious way so as not to form nitrate. It has been suggested that you don't even need a skimmer. Lots of reef rock and that's it! Maybe some aquarists can make this work for more than two weeks, but I do not think experimenting with such a precarious—yes, precarious!—system (and that is using the word loosely) is something to do unless you are ready to gamble a lot of reef creatures and money. It has been suggested that those who do not agree with this approach simply do not understand the chemistry of reef rock. In all humility, I have to admit I do not understand the mysterious new age chemistry alluded to by some of the proponents of this approach. If you have a high nitrate concentration, it makes more sense to find a way to remove the nitrate, either by religious water changes or some kind of denitrification filter or agent. If you have too much nitrate, seek to improve the denitrifying capacity of your rock and filter material, not short circuit your nitrifying filter. Also, seek to remove ammonia before it is converted to nitrite: a well vented wet-dry or ammonia tower can have significant impact by venting free ammonia directly to the air; also enhanced chemical filtration and skimming can remove many amino-organics before they are bacterially converted to ammonia. It is also important to consider that nitrate in itself is not likely the real problem, but rather other not easily measured impurities for which nitrate is a useful marker. All the more reason not to neglect water changes and to consider supplemental chemical, bacterial, and algal filtration.
Reef keeping is as much an art as it is a science. There is no single best way to practice this art, but any approach should be viewed with caution when it evokes the suspension of basic chemical principles or plain good sense.