Dry Food vs Frozen Nitrates/Phosphates

[djbetterly]

Does dry food end up yielding higher nitrates/phosphates than frozen?

I ask because I typically notice higher levels of nitrates/phosphates when using dry food (Neptune cross over diet) vs when I use frozen.

 

[Brew12]

Does dry food end up yielding higher nitrates/phosphates than frozen?

I ask because I typically notice higher levels of nitrates/phosphates when using dry food (Neptune cross over diet) vs when I use frozen.

It is a tough question to answer because it largely depends on the dry food as compared to the frozen.

One possibility is that the dry food you are using is more nutrient dense than the frozen you use, and you are inadvertently adding more total food to your system. It would be interesting to thaw and dry your normal portion of frozen food then weight it and compare it to the weight of your dry food. I'm guessing the frozen would end up lighter.

 

[djbetterly]

hmmm...if I could figure out a way to dry the frozen food out without it stinking to all ***L I'd totally do that experiment.

 

[jda]

There are two things working here...

First, the frozen food has much of it's volume in water. In a dry-weight comparison, they are going to be about the same with protein, fat, phosphorus, etc.. Your fish fill up on water when you feed them frozen. Your fish do not need to eat as many pellets.

Second, the "juice" from the frozen food cannot be consumed by the fish. If you have filter feeding inverts, then they probably love this. If not, then rinse it all off or pour the juice down the drain for less N and P into your tank.

 

[Randy Holmes-Farley Verified Community Expert]

Just to be clear, the N and P in foods are not impurities. They are integral ingredients of the biomolecules in tissue based foods and cannot be removed. For example, there is at least one and often 2 or more nitrogen molecules in every amino acid in every protein, and those will end up as nitrate if the protein is metabolized.

Similarly, phosphate is part of many biomolecules in every cell, such as DNA, RNA, phospholipids, and many proteins.

IF you use a food that contains fish meal, then it may contain excess phosphate due to bones, which have a lot of phosphorus in them.

I show the phosphorus levels in many foods here:

Aquarium Chemistry: Phosphate And Math: Yes You Need To Understand Both
https://www.advancedaquarist.com/2012/3/chemistry