Second guessing my water change practices

[Yellow_donkey]

So I have a 60-gallon tank that is nearing 2 years old. Over the past 18 months I have strived to water change 50% once a month and have been pretty consistent with some months maybe going 45 days but over the past 6 months I have been more stringent, and have been hitting the 30 day mark. Also, my sump is a 40 breeder so with plumbing and sump and I have roughly 80 to 90 gallons of water in the system at any given time.

My RODI has worked well. I have always changed the cartridges every 6 months and a year on the membrane and watched my TDS on my DI Mix Beds.

My issue is this, 2 months ago roughly I had a water change that resulted in current brown film on the glass and a diatom bloom on the sand I must clear/cover over everyday so the tank doesn't look like crap. I am wondering with my water change regimen which worked well until just recently, am I replacing too much water in the system, resulting in what I would consider a newly cycled tank diatom breakout, but my ammonia is 0, Nitrite is 0, Nitrate is 10 and phospahte is low with use of RowAPhose and a huge cheato ball in sump.

So either I disrupted the bacterial load with too frequent and too large water changes and/or I also noticed the end of my RODI fill, 2 months ago I had a TDS of 2 to 4 at the end of the fillup of my 45 gallon Rubbermaid. I was worried but end the end went with the batch of RODI as I didnt want to waste it. This may have been a cause of my issue as well.

I ran ICP-OES a few months back on my RODI and the results were zero across the board aside for Silicon which was very high. Does this relate to silicate? The fuel source for Diatoms?

So, currently, I am fighting the daily buildup of brown on my sand and getting ready to do my next improved 40gallon water change. As I suspected the RODI may have been the culprit I have added a 10' Anion and Cation beds, priot to my original double mix bed on my rodi and after reading further saw that my muni 45 psi supply was way to low and have added a booster pump as well. So I have new batch of fresh water ready to go for another change in hope to avoid the possibility that my RODI has caused this issue but if it did, to make sure it doesn't happen again.

As a side I am loving this new RODI setup as well. Who would have known 80 psi versus 45 would have made such a huge difference. My post membrane TDS at muni supplied 45 psi was roughly 60 to 80 and that went right into my double mixed bed which depleted pretty quickly, couple water changes at the most and one 10" would need replaced.

But now with my RODI booster pump at 80 PSI I am getting 9, post membrane, 9 only, that a huge reduction by the membrane only! And that is before it ever touches any DI material. It then enters the Anion at 9 and comes out at 0, as Anion is Silicate bonding and what would grab my high Silicone levels possibly, if those two are related. In the end, my Cation and double mixed bed are all fed with 0 TDS water already (for a whole 40 gallons which prior would have depleted at least 5" of of single DI mixed bed alone)! So not only will I get super 0 water I will save a good bit of time and money on mixed bed DI replacement.

So that is the main step I have taken to try to prevent this from happening again, but I still have to fight the issue in place which will be partial sand bed removal, cleaning and reintroduction over the next couple of months.

Through this whole process and the reason for this post is my other concern that this may all be possibly due to to high a water change amount, is this to much change for the system. I also read about folks doing 90 to 100% changes and no issues for whatever reasons. But still his is nagging me.

What do you'll think. Could a 2 TDS batch of water that sneaked by me cause a diatom bloom or am I changing too much water at one time?

Also, anyone who has a post membrane TDS higher then 10, look into a booster pump, those RO membranes are supposed to run at 60 PSI or higher and they preform much better, I had no idea!

Thank everyone, look forward to thoughts or experience with slightly higher than 0 TDS tank issues?

 

[mcgyvr]

Excessive silicates has most certainly been a stated reason for diatom issues...
Typically the diatoms will consume the excess and as long as you aren't adding more the diatoms will die out..

As long as you are matching parameters the amount of water you change at one time shouldn't matter.

I believe there are 2 forms of silica reactive/unreactive.. I believe reactive is part of a TDS result but unreactive is not..

Now that you have made changes it will be interesting to see if your diatom problem goes away..
I wouldn't think you need to change out the sand bed or anything as the diatoms will just consume what they can and deplete the supply..

 

[Yellow_donkey]

Excessive silicates has most certainly been a stated reason for diatom issues...
Typically the diatoms will consume the excess and as long as you aren't adding more the diatoms will die out..

As long as you are matching parameters the amount of water you change at one time shouldn't matter.

I believe there are 2 forms of silica reactive/unreactive.. I believe reactive is part of a TDS result but unreactive is not..

Now that you have made changes it will be interesting to see if your diatom problem goes away..
I wouldn't think you need to change out the sand bed or anything as the diatoms will just consume what they can and deplete the supply..

Thanks for the reply MC, I did infact implement the new practices with the Anion and Cation 10" beds prior to my double 10" mixed beds, all of which on BRS if anyone needs these pre de-Ion mixes and sure thing, a single water change, my once every 30 day water change fixed the issue 100% (diatoms).

I fought that for about 90 days after a bad batch of water got through, and with bad I am talking 2 to 4 TDS reading but like I said I have super high Silicone from municipal supply and that did it. So I changed roughly 50% in this last month (single change) with Anion and Cations added and wham, all film algea is back to super green (thin, but you know the stuff we get on our glass built up over 4 to 5 days, and nothing on sand, its gone back to non-clumping crystal white again.)

So My take aways from this are as folows:

All RODI users should consider two bads before their mixed bed; a Anion then Cation if your using/exhausting more than 10% of Mixed bed every 50 gallon batch of water. (I was using 25% or more per 50 gallons of water.

Dont skip if you get a 2 to 4 TDS on your batch of water and you want to try to use it. Throw it out or drink it and make new, 0 TDS only into tank. (I make our drinking water for the water cooler, I dont run that through the de-ion as we need some minerals in our own intake water, but a batch of 0 is ok TO drink as long as tghat is the only thing you ever drink)

Add a booster pumps, but first add a pressure gauge. If your supply into membrane is less than 60 psi, add a booster pump. Adding a booster pump make the membrane work much much much better, it alone gets TDS below 10, when it was over 100 before I added it. One thing to watch, say you let RODI sit for 3 weeks in -between water batches, disconnect your output (after the membrane and before the Anion/Cation or Mixed Beds when you first start it back up) that next startup TDS will be super super high, so flush that water out for 30 to 60 seconds and then reconnect flow into whatever single or mix bed de-ions you have, so you dont flush 300+ TDS into them for a couple of minutes at the startup, thats just a waste of money.

Hope this helps others! Happy to help if anyone has any questions or if I can do anything better let em know!

 

[Drewbe147]

Lots of useful information here. Thank you for sharing your experiences and observations