Any benefit to dosing phosphate during fishless cycle?

[Spare time]

You are correct. Nitrifying bacteria do require a small amount of phosphate, this is why bottled bacteria manufacturers recommend against starting the early tank cycle with a refugium, or GFO/phosban bit to instead wait until you visibly see algae growing.

That was sorta what I was getting at with my post in that some people immediately use filter material that comes with a tank or filter, which sometimes has phosphate removers.

 

[fishmonkey]

Yeah phosphate is only an issue for a very small number of tanks.

Although all living beings require phosphorous (literally DNA and RNA both contains phosphorous), for the most cases phosphate addition is not needed. For saltwater aquariums despite using RO, it seems like whatever little amount may be in salt mixes, etc. would be plenty.

For freshwater aquariums, enough phosphate seems to come through tap water that it never is an issue. The only time it may matter is if people use RO water to set up freshwater aquariums, which even after remineralization (depending on the method) may not contain enough phosphorous for the nitrifiers to utilize.

But yeah. That's why generally one only needs to dose ammonia when fishless cycling - most of the crucial elements (carbon, hydrogen, and oxygen) can be obtained from the water (specifically the water itself, and inorganic substrates such as carbon dioxide), while nitrogen can be obtained from not least of all the ammonia.

It's also why you don't even need to add fish food or anything like that - nitrifiers are generally known to be obligatorily autotrophic and cannot use organic substrates as a carbon source anyways.

The thing is I let like 3/4 of my dry Marco rock settle in rodi water for 4 or 5 days. It’s day 5 of my cycle after adding xlm and I’m around 2 ppm ammonia and have very little nitrite. I might check for phosphate just out of curiosity