If you are getting algae, use Phosban in a reactor,increase oxygen and ensure high alkalinity and get more Herbivores!
Algae problems? The reason has a lot to do with alkalinity in most cases, but it can also be lack of herbivores, phosphate in the rock and sand to a lesser extent, and also other factors such as elevated CO2 in the house or biological instability (as when an aquarium is first set up or if it is heavily disturbed, for example by gravel vacuuming). Sometimes algae are just stubborn and it takes a long time to make a change happen. ;-)
If you were having a problem with no change of phosphate level, several possibilities exist:
1. test error
2. high source of phosphate in the system (from the top-off water, from the rock or sand, from activated carbon, from food)
3. competing ions or adsorbable substances in high concentration: PhosBan also adsorbs silicate and dissolved organics. In an aquarium with extremely high silicate and or dissolved organics the phosphate adsorbing capacity may be reduced. This is rare but possible.
I suggest you use reactors! The difference with reactors is that they are upflow, so they don't trap dirt, or can easily be flushed to release dirt, and they typically operate with much lower flow rates (60 lt per hour for example), an exception being the use with NPX Bioplastics which is much higher flow, but no chance to trap anything because the media is tumbling.
If you want to use mechanical filtration, a filter sock in the sump for the drain from the tank, changed (rotated with a fresh clean sock-- the dirty one being rinsed and soaked in bleach, then rinsed and dried) every few days, is the best way. Letting the detritus circulate instead of trapping it in a canister or sock is also a way to manage it since it will end up getting trapped in the protein skimmer or sand.
For alkalinity maintenance I recommend calcium reactors (but of course not for all customers), kalkwasser, and two-part calcium and alkalinity maintenance systems. Kalkwasser dosing has some very positive effects against algae growth too-- apparently because it improves protein skimming efficiency, and I believe it also has to do with night-time pH levels being higher. Naturally I recommend our product C-Balance for the two-part dosing system. for most customers a combination of kalkwasser and C-Balance is ideal, or if the kalkwasser is not practical for them, C-Balance alone can be used.
Phosphate problems could also be related to phosphate levels in the rocks themselves. That is a problem that will go away in time if the phosphate in the water is kept low and the alkalinity high so that coralline algae coat the rocks and essentially lock in the phosphate so that it is not available on the surface. Smaller tanks give fewer options for herbivores, but Trochus or Turbo snails may help.
There are nitrate affects on algae too. Have you tried NPX Bioplastics yet? I recommend it for tanks with nitrate problems, but you must have a good protein skimmer, and you must have a surface skimming overflow to assure high oxygen levels. The media is installed in our reactor with the NPX screens used in place of the sponges. You need a strong enough pump to keep the media tumbling. The idea is that NPX is a food for bacteria-- the bacteria eat the food and as they grow they take up nitrate and some phosphate from the water. The tumbling causes some bacteria to shed off the media and they end up in the water where they can be trapped by a protein skimmer. This way the nutrients they have removed from the water can be exported permanently. The dosage rate is about 1ml per liter, though you can start with half that amount and increase as needed. The media takes about 6 months or more to be consumed by the bacteria, so you top-off periodically.
Tips from Julian Sprung