Theory: Would Decreasing Water Chage Volume Cause Diatome Bloom

[RussC]

I have a 100 gallon volume setup. I use Red Sea Pro salt. When mixed, its about 11.4 ALK and 450 ish Calcium. My system wasn't running at those numbers, so every two weeks when I did a water change it would sway my numbers. I like it consistent. In an effort to stabilize water parameters, I have reduced from a 20 gallon water change to a 10 gallon water change. It just so happened at the same time, I bumped up my lights 3%. Now I've got a mean brown diatom bloom on my substrate. Could this be because I'm removing less nutrients with smaller water changes (in addition to more light)?

I know light is playing a factor because I can see the difference in growth of the algae (or lack thereof) under my big leather. My phosphates are measuring zero. But I know there are nutrients in that tank for no other reason than I feed frozen food every other day. But I've done that for a year now. So inquiring minds want to know. What are your thoughts, R2R?

 

[oceanfreak09]

I would say any cut back on Maintenance would have ill effects. I try to find out what works and stick to that. Whenever I fall off ,The problems start. [emoji2]

 

[chipmunkofdoom2]

Now I've got a mean brown diatom bloom on my substrate. Could this be because I'm removing less nutrients with smaller water changes (in addition to more light)?

The water change decrease is pretty small. For example, if your nitrates are 10 ppm and phosphates are 0.5 ppm, after a 20% water change they would be 8ppm and 0.4 ppm respectively. After a 10% change, they would be 9ppm and 0.45ppm respectively. The difference between N = 8ppm or 9ppm and P = 0.4 ppm and 0.45 ppm is relatively small.

3% increase in lighting intensity is also really small. If you previously ran 300 PAR in the middle of your tank, after a 3% increase, your tank would now have 309 PAR in the middle.

I think the balance for nutrients, trace elements and light is a lot more nuanced than we are aware of, partially because of our inability measure trace elements accurately and in real-time, but also partly because we just don't understand all the things going on in our reef tanks. Perhaps your nutrient and light balance was precise enough that it just kept diatoms at bay, and by changing both of those, you just very slightly tipped the scale in favor of diatoms. Perhaps it's not related to either of these things. It's hard to say.

If the calcium and alkalinity of your source water is too high, why not change salt mixes instead of decreasing water change volume? Red Sea's blue bucket has lower values of both and would be much more likely to match your tank chemistry.

 

[saltyfilmfolks]

What type of diatoms are they? The standard dusty ones or a slimey one?

 

[RussC]

Chipmunk, I like your point. Makes sense.

I guess I’m experimenting a little. I almost went with the Red Sea Blue bucket. Almost. Then decided I’ll increase my Alk and Ca a little with Pro and maintain it at that level rather than decreasing it using the blue bucket. The trade off is slightly less volume on my water Change to keep it more stable.

Saltyfilm, id call these diatoms brown. They actually look hairy and I’ve noticed some clumps. Figured I’d throw a lawnmower blenny in there and let him go to town.

 

[saltyfilmfolks]

Chipmunk, I like your point. Makes sense.

I guess I’m experimenting a little. I almost went with the Red Sea Blue bucket. Almost. Then decided I’ll increase my Alk and Ca a little with Pro and maintain it at that level rather than decreasing it using the blue bucket. The trade off is slightly less volume on my water Change to keep it more stable.

Saltyfilm, id call these diatoms brown. They actually look hairy and I’ve noticed some clumps. Figured I’d throw a lawnmower blenny in there and let him go to town.

Chonks.

Our friend Dana induced a slimy diatom bloom by adding a blue led strip.
I highly doubt the salt alk thing is the problem. I have for years used NSW. Then I swapped to instant ocean a while , starting dosing and got to 16, did wc. Switched to fritz pro (8) use NSW again , some Io etc.
so honesty using NSW I’m actualy adding diatoms. But have never had a bloom.
I’d actually look at your RODI. It’s Not uncommon for many reefers to report dusty blooms even when the TDS is reading zero or teetering at zero and one. Happens to me this year but I got cyanos and a few other oddities instead.
I’d wager your feeding the diatoms silicates.
If your not running gfo you might consider it.