Dry rock leeching phosphate

I have brown bushy algae completely taking over my tank. I have removed it physically twice, run chemipure elite, Seachem sea gel in a reactor and added a HOB that doubles my mechanical filtration with sea gel as well. It keeps growing.

The tank is 6 months old and I have had this for about 2 months now. I have come to the conclusion that it is due to phosphate leeching out of the Marco dry rock. I did not do anything but rinse it before using it in the new tank.

Innovative Marine 38 Gallon
92 Watt dual spectrum IM lighting
Hydor Nano skimmer
IM media reactor with sea gel
Aquaclear 70 HOB with sea gel
inTank media basket with floss/purigen/chemipure elite

I am going to change over to seachem phosguard instead of sea gel and keep removing it weekly with the 15% water change.

How long do you think it will take to work out or will I need to just pull all the rock and cook it? What procedure would I use to cook it?

 

What is your water source? What inhabitants do you have, what are you feeding, how much, and how often? Can you post a pic? Sounds like you might have bryopsis, a very low-nutrient pest algae. A few days of darkness or an elevated mag level will usually get rid of it. I've never used Marco rocks personally, but I've never heard of anyone having a problem. In fact, they get a lot of positive reviews and recommendations.

 

Water source - RO water, Seachem Salinity salt mix
Feeding - mysis, angel formula II every other day along with a drop of phytoplanktin. 1/2 cube of each. I actually only put in less than a full cube and rinse it after thawing. I feed spectrum pellets on alternate days. Only enough to fill them up.
Inhabitants - 2 clowns, 1 royal gramma, 1 Coral Beauty Pymy Angel, 2 small zoos, 1 anemone
CUC - coral banded shrimp, 10 hermit crabs, 5 scarlet hermit crabs, 2 turbos, astrea, nesarious

Weekly 5 gallon water change, daily water top off using RO. Not dosing anything.

Filters - 2 media baskets with floss/purigen/chemipure elite, Media reactor with sea gel, HOB power filter with floss and sea gel. I was running a Hydor slim skim nano skimmer but it is off for the moment.

The tank is a 38 gallon all in one. I just added an additional pump for a total of 952GPH not including any help from the HOB filter (259 gph).

Temp - 79-80
Ammonia - 0
Nitrite - 0
Nitrate - 0
PH - Daily fluctuation of 8.2 to 8.4

I really like the Marco rock and am using some from the same batch in another tank with no issues. I just can't figure out what the nutrient source is that would so totally overwhelm the tank. Nothing I do even slows it down. I have removed a ton of it physically twice and will be doing so again tomorrow.

 

For starters how about a tang/rabbit to keep the algae at bay as much as possible.

 

not in a 38 gallon IMO and they don't eat ALL algae types

Pic would help to determine a route of action. DO NOT COOK YOUR ROCK. there was a thread a while back about a man and his wife having to go to the hospital after cooking rock.

with all that feeding, it wouldn't hurt to turn the skimmer back on either.

 

After calculatuing the amount of space taken up by rock,powerheads,substrate,fish, snails,crabs, and a shrimp you at most have 28 gallons of water. I think the only thing leaching Phosphates is the 24 inhabitants you have.