Did I kill my RO membrane? Brown dusting after water change.

doma · 08/11/2010, 12:28 PM

Hi all-
I've been using my RO/DI unit for 1 year now. I'm wondering if I need to get a new membrane.

The reason is after a water change my tank will within hours develop a brown dusting over everything. This started happening about 2 months ago. Using an eyedropper I can puff water at the brown and it blows away into the water and disappears.

HOWEVER... my TDS meter still shows zero on the output side of the RO/DI unit. The input side shows 18ppm. Which makes me think it's fine and something else is wrong which causes my tank to react to the fresh RO/DI salt water in a way that dusts everything brown.

So... my question for you experienced reefers is ... if the TDS meter says zero is the membrane still fine? It's supposed to be a 50 gpd unit but I let it dry out once and it has only flowed at about 10 gpd since that event. If the TDS meter tells no lies then what else could it be?

I have tested the phosphate of the RO/DI water ... it's zero.

Tank specs:
55gal disp, 30 gal sump
Skimmer, phosban reactor (with brown posban ... hmm)
dKH: 8
Ca: 360
Temp: 78 (on a controller ... rock steady day long)
trate and trite: 0
ammonia: 0
phos: 0
SG: 1.025
Algae: everywhere ... I'm in the middle of an algae battle which started about 3 months ago out of nowhere. I'm toothbrushing the rocks and filter socking the results.
SPS: very happy, colorful, and growing fine.
Xenia: were happy but took a sharp turn for worse about 2 months ago for unexplained reasons.
Cocco Worm: was happy but took a sharp turn for worse about 2 months ago as well. He's down to only a few gill hairs left.

thanks for any advice. I'm thinking of replacing the RO membrane ... but maybe its fine (TDS thinks so??) and something else is causing the brown dust of doom (leaking phosban??)

thanks-
-doma

DustinB · 08/11/2010, 12:42 PM

You sure the brown dust isn't diatoms?

If your nitrates and phosphates are truly 0, then that's probably why your xenia and worms aren't doing well. You have no nutrients in the water. Try feeding rod's food or something similar. Probably some phyto too.

doma · 08/11/2010, 12:53 PM

Yes, someone had suggested diatoms re the brown dust. Which made me think something that diatoms feed on is getting past the RO membrane. Or the membrane is doing great and diatoms simply love fresh water changes. :-)

I've been feeding the few fish and hoping (guessing?) that any leftovers would feed the xenia / worm. I'll look into Rod's food and phyto as you suggest. I used to drip in a food called 'oyster feast' last year but stopped - would that kind of product also be good for the xenia & worm?

thanks-
-dom

08/11/2010, 12:28 PM	#1
doma Registered Member Join Date: Jun 2009 Posts: 14	Did I kill my RO membrane? Brown dusting after water change. Hi all- I've been using my RO/DI unit for 1 year now. I'm wondering if I need to get a new membrane. The reason is after a water change my tank will within hours develop a brown dusting over everything. This started happening about 2 months ago. Using an eyedropper I can puff water at the brown and it blows away into the water and disappears. HOWEVER... my TDS meter still shows zero on the output side of the RO/DI unit. The input side shows 18ppm. Which makes me think it's fine and something else is wrong which causes my tank to react to the fresh RO/DI salt water in a way that dusts everything brown. So... my question for you experienced reefers is ... if the TDS meter says zero is the membrane still fine? It's supposed to be a 50 gpd unit but I let it dry out once and it has only flowed at about 10 gpd since that event. If the TDS meter tells no lies then what else could it be? I have tested the phosphate of the RO/DI water ... it's zero. Tank specs: 55gal disp, 30 gal sump Skimmer, phosban reactor (with brown posban ... hmm) dKH: 8 Ca: 360 Temp: 78 (on a controller ... rock steady day long) trate and trite: 0 ammonia: 0 phos: 0 SG: 1.025 Algae: everywhere ... I'm in the middle of an algae battle which started about 3 months ago out of nowhere. I'm toothbrushing the rocks and filter socking the results. SPS: very happy, colorful, and growing fine. Xenia: were happy but took a sharp turn for worse about 2 months ago for unexplained reasons. Cocco Worm: was happy but took a sharp turn for worse about 2 months ago as well. He's down to only a few gill hairs left. thanks for any advice. I'm thinking of replacing the RO membrane ... but maybe its fine (TDS thinks so??) and something else is causing the brown dust of doom (leaking phosban??) thanks- -doma

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08/11/2010, 12:42 PM	#2
DustinB Registered Member Join Date: Apr 2010 Location: Texas Posts: 1,532	You sure the brown dust isn't diatoms? If your nitrates and phosphates are truly 0, then that's probably why your xenia and worms aren't doing well. You have no nutrients in the water. Try feeding rod's food or something similar. Probably some phyto too.

08/11/2010, 12:53 PM	#3
doma Registered Member Join Date: Jun 2009 Posts: 14	Yes, someone had suggested diatoms re the brown dust. Which made me think something that diatoms feed on is getting past the RO membrane. Or the membrane is doing great and diatoms simply love fresh water changes. :-) I've been feeding the few fish and hoping (guessing?) that any leftovers would feed the xenia / worm. I'll look into Rod's food and phyto as you suggest. I used to drip in a food called 'oyster feast' last year but stopped - would that kind of product also be good for the xenia & worm? thanks- -dom