effects of aquasoil on phosphate levels
As the title states, I will be doing an experiment to see the effects aquasoil and aquasoil with a power sand layer has on Phosphate levels in the water column. Iím doing this for several reasons. First, I like to know what is going on in my tank, Second is for those who believe there should be some amount of phosphate in the water column and to aid them in coming up with a rough dosing schedule without having to do daily testing in the beginning like I had to. I donít believe there has to be an algae phase like most people experience with a new tank setup with aquasoil. I believe the rough starts are due to the water column being phosphate limited at the same time a rich nitrogen source is being leached into the water column.
I currently have two tanks setup. Both tanks are pressurized co2 injected to a 1.3 ph drop. Both tanks have the same amount of lighting. The main tank is a 180 gallon with a 1inch power sand layer and a 3inch aquasoil layer. The second tank is a 40 gallon with a 4inch aquasoil layer with no power sand. Both tanks followed ADAís recommended water change schedule.
The 180 gallon has been running for about 3 months and I dosed kh2po4 from the beginning along with K2s04 and burrs micro mix. I have had zero algae issues from the beginning. I had a pretty decent diatom phase two weeks in and it lasted about 2- 2 Ĺ weeks. Once that disappeared I have had no other algae outbreaks. Half of the tank was planted with emmersed grown plants and even with that I had zero issues with algae.
The 40 gallon has been running about 4 weeks. I dose K2s04 at water change and burrs micro mix daily. This tank has received no phosphate dosing. This tank was heavily planted with trimmings from the 180 that were in perfect health. It has been a night and day difference between the two tank startups. This tank has multiple algae issues, and the health of the plants are nowhere near the health of the plants in the 180. I have cleaned the glass on the 180 maybe 4 times in roughly 3 months. The 40 gallon, if it was a display tank I would have to do it every couple days. The tank is starting to turn around now and when I do the next big hack and clean everything, It will look pretty good.
I decided to dose phosphate in the 180 a few days after planting because rotala wallichi was showing signs of stunting. I tested all water parameters and noticed phosphate was undetectable. So I dosed an EI level of kh2p04. Within a couple hours I could see the growth tips of the wallichi return to normal. When I say stunting and unstunting in couple hours Iím talking very minor differences in the growing tip. Within less than 1 photo period the wallichi would start showing abnormal signs again. I tested Phosphate again and it was undetectable. Long story short, this went on for weeks and I kept raising my dose of kh2p04 till I could have a detectable amount of phosphate before the next dose. This was usually only around .02-.05ppm using a lamotte low range phosphate kit. The dose I came up with was 5ppm per day (35ppm) per week.
To me 35ppm per week of kh2po4 sounds absurd and didnít understand and still donít understand how this could be possible, but for me to have an algae free startup with healthy plants, this is what it took. This is one of the reasons I setup the 40 gallon, to see what would happen If I didnít keep a measurable amount of phosphate in the water column. I believe having a measurable amount of phosphate in the water column, even if its only .05ppm means there is excess for the plants to access if needed and for me that required 35ppm per week.
I plan on setting up two 5 gallon buckets, one with just aquasoil and one with aquasoil and power sand. I will place a circulation pump in both buckets and start off with EI dosing of phosphate and test the results 4 hours into a photo period and at the end of a photo period. I will keep raising levels to probably about 10ppm per dose to see what happens. I havenít decided how long I will continue this experiment, but most likely till the powersand sponge is done sucking up phosphate. Hopefully this will help someone come up with a phosphate dosing schedule for a new aquasoil tank who believes there should be phosphate in the water column.