Nutriants
 

i have been told that i have "nutriant rich water" because i have a bit of the thick black alge. how can i get rid of this problem and keep my tank not so nutriant rich??!! my tank is a 20 gallon.

Use RO/DI water, feed less and in smaller amounts. Setup a refugium for nutrient export stuffed with macro algaes.... the black algae your mentioning sounds like dinoflagelettes? (sp???) nasty stuff from what I have heard.

Those are just a couple suggestions

Lets add 2 things to what OCDP said:

More (and larger) water changes... More skimming.

my tank is 100% RO/DI water..... i change about 10-15% weekly. how often SHOULD i be doing it?

20g tank + $250 wourth of fish = nutrient problem

67g tank = pricless

i only have 4 fish...im getting a 90 soon. 67 is too small!!!

Oh yeah, forgot about the skimming... that will definitely help you out.

If your using true, pure RO/DI water you really shouldn't be experiencing such nutrient problems. You either feed too much, too often... have too high of a bioload for you to handle... or there is something feeding the nutrients... ie, phosphates and nitrates. But if you do use RO/DI and do weekly changes.. that should be sufficient.

I would get a skimmer (a good one..) and skim really wet for a while... feed less, (every second or third day) in very small amounts.

I use a 20g tank, and have had slight nutrient issues... but with heavy skimming, frequent water changes and small feedings my tank looks just fine without nuisance algaes.

Four fish doesn't mean much - Four lions, vs four gobies are two radically different bioloads.

Not all RO is the same, check TDS readings of that water.

You should really have a skimmer, 4 of any kind of fish in a 20g is quite a bioload. A substantial hunk of graciliara, or chaeto would really help you on your way.

10-15% water changes weekly ought to be adequate, but...
...alot of absent info here.

What do your water quality tests say?
How old is this set up?
A bit of black algae? How much is a bit?
What kind of algae? Have you tried to ID it? Take a picture and post?
Four fish? What type? How big?
What else have you got in the tank? Inverts? Corals? Live Rock? (more than just fish contribute to a bio-load).
Are you skimming?

Cheers,

ok, i have 2 percs, 1 six line wrasse, and 1 manderine draggonette. all very small. i bit of alge as in a patch about 3 inches long and 2 inches wide. i am skimming but it is a very crappy skimmer. what would be good for the 20 ????? i have a squamosa clam in there, TONS of different zoos, finger leather, ricordia, conch, snails, crabs, emerald crab, various polyps, and feather duster.... i think im missing a few things....but i cant think of them... o ya a bta.... i THINK thats it