Years ago I had a 120 gal well-established reef tank with alot of pukani live rock and a 4 inch sand bed. Phosphate control was my primary issue. In my recollection, nitrate levels were consistently low or undetectable. Perhaps it was all the live rock and/or sand bed. I used GFO but then switched over to chaeto and this worked very well.
I moved to S. Korea for a few years and only recently started getting back into the hobby. My current tank is a little 15gal, pretty immature at less than a year old. It's bare-bottom. Nitrate consistently creeps up to 20ppm before I do a water change, phosphorus is very stable usually 15-20 ppb (0.05 - 0.06 ppm phosphate). I don't have any phosphate control in place (other than coral). So, a completely different experience than before.
I am currently building a new setup with two tanks, total of 120 gallons, and have been experimenting with phyto in anticipation of the project. I want one of the tanks to have a lot of filter feeders. It will be awhile before this happens so right now I'm just trying out ideas with the phyto. One idea I had is to use a max density phyto culture for weekly water changes.
I know plenty of people have theorized about using phyto for nitrate/phosphate control (basically in place of chaeto), but since it's not a common practice I expect there are challenges to doing so. I've tested using a tetraselmis culture and thought I'd share my results.
FIrst thing I did was simply start a new tetraselmis culture in a 5 gallon bucket and measure nitrate and phosphorus levels over time. I used an api nitrate kit and hanna phosphorus ulr checker. Also I should note that I centrifuged the samples to separate out phyto prior to water testing, otherwise the green water would prevent accurate readings.
Admittedly I should have tested more often but wasn't expecting the levels to change so rapidly. In particular the phosphate, it appears tetraselmis consumes phosphate very rapidly. Next week I'm planning to run it again a little more controlled with daily readings, and once nitrate gets below 10 ppm I can switch to a red sea nitrate pro kit to get more precision on the nitrate readings.
At any rate, it seems to me adding phyto culture to a reef tank would add significant nitrate to the tank, at least using tetraselmis and standard f/2 media. I know of tanks run at 20 ppm nitrate but it's not a natural level, and if I were to add large amounts of tetraselmis culture water to my tank I suspect it would depress phosphate but elevate nitrate levels unsustainably. However this can be controlled by adding additional phosphate to the culture. With adjustments I think I could create a culture with undetectable nitrate/phosphate, and therefore could add relatively large amounts of living phyto without adding nitrate or phosphate to the reef tank. Alternatively, I could shoot for whatever levels desired by tweaking the fertilizer elements in my culture (e.g. if the tank tends to run high nitrate, set the culture to 0 nitrate but some phosphate to continue feeding the phyto and bring down tank's nitrate level). The phyto would then serve the same purpose as chaeto or an algae turf scrubber for nutrient control.
So the theory is using this method as an alternative to both the typical weekly water change and a refugium with chaeto.
Crazy idea or perhaps workable? Have other people tried this, and if so what were the problems/challenges?
Anticipated/potential challenges:
I moved to S. Korea for a few years and only recently started getting back into the hobby. My current tank is a little 15gal, pretty immature at less than a year old. It's bare-bottom. Nitrate consistently creeps up to 20ppm before I do a water change, phosphorus is very stable usually 15-20 ppb (0.05 - 0.06 ppm phosphate). I don't have any phosphate control in place (other than coral). So, a completely different experience than before.
I am currently building a new setup with two tanks, total of 120 gallons, and have been experimenting with phyto in anticipation of the project. I want one of the tanks to have a lot of filter feeders. It will be awhile before this happens so right now I'm just trying out ideas with the phyto. One idea I had is to use a max density phyto culture for weekly water changes.
I know plenty of people have theorized about using phyto for nitrate/phosphate control (basically in place of chaeto), but since it's not a common practice I expect there are challenges to doing so. I've tested using a tetraselmis culture and thought I'd share my results.
FIrst thing I did was simply start a new tetraselmis culture in a 5 gallon bucket and measure nitrate and phosphorus levels over time. I used an api nitrate kit and hanna phosphorus ulr checker. Also I should note that I centrifuged the samples to separate out phyto prior to water testing, otherwise the green water would prevent accurate readings.
- Day 0 - 5 gal fresh salt water 1.026 sg with 7.5 ml f2 fertilizer (recommended level per florida aqua farms):
- Nitrate: 80 ppm, phosphorus: off scale (>200 ppb)
- Day 4
- Nitrate: 20 ppm, phosphorus: 8 ppb
- Day 5
- Nitrate: 20 ppm, phosphorus: undetectable (measured 0 ppb)
- Nitrate: 20 ppm, phosphorus: undetectable (measured 0 ppb)
- Day 7
- Nitrate: undetectable (< 10 ppm per api test kit), phosphorus: undetectable (0 ppb)
Admittedly I should have tested more often but wasn't expecting the levels to change so rapidly. In particular the phosphate, it appears tetraselmis consumes phosphate very rapidly. Next week I'm planning to run it again a little more controlled with daily readings, and once nitrate gets below 10 ppm I can switch to a red sea nitrate pro kit to get more precision on the nitrate readings.
At any rate, it seems to me adding phyto culture to a reef tank would add significant nitrate to the tank, at least using tetraselmis and standard f/2 media. I know of tanks run at 20 ppm nitrate but it's not a natural level, and if I were to add large amounts of tetraselmis culture water to my tank I suspect it would depress phosphate but elevate nitrate levels unsustainably. However this can be controlled by adding additional phosphate to the culture. With adjustments I think I could create a culture with undetectable nitrate/phosphate, and therefore could add relatively large amounts of living phyto without adding nitrate or phosphate to the reef tank. Alternatively, I could shoot for whatever levels desired by tweaking the fertilizer elements in my culture (e.g. if the tank tends to run high nitrate, set the culture to 0 nitrate but some phosphate to continue feeding the phyto and bring down tank's nitrate level). The phyto would then serve the same purpose as chaeto or an algae turf scrubber for nutrient control.
So the theory is using this method as an alternative to both the typical weekly water change and a refugium with chaeto.
Crazy idea or perhaps workable? Have other people tried this, and if so what were the problems/challenges?
Anticipated/potential challenges:
- Depletion of minor/trace elements by phyto culture. Can check this via ICP, then potentially address with supplements.
- How stable/consistent is the culture? If I follow the exact same procedure, I'm hoping to get the same water parameters with the goal to do water changes and filter feedings in one relatively easy process. Water changes need to be stable and consistent, but adding a living organism to the mix will likely add variability.
- Would the phyto get eaten too quickly or too slowly? My system will have a UV sterilizer, so if I want this would prevent a phyto bloom in the reef tank. That could be a problem at the beginning, before there were many filter feeders but after awhile with such a food source available filter feeders would explode and then maybe eat the phyto within hours, reducing its effectiveness as a chaeto alternative. I suppose I could still run a chaeto refugium, it's not like this is very labor-intensive and I know the method works.