Could I get some suggestions on using Fox Farm fertilizers

I started using Fox Farm fertilizers and was looking for some suggestions on how much and how often to apply to my Autoflowers? I wanted to ask what more experience growers have experienced when using these fertilizers.

Also, using Cal-Mag for my plants? Good idea? Thank you everyone :blush:

Weekly feeding amounts, per FF. The schedule is very aggressive and often leads to nute burn. I would start out with half the recommended amounts.


Thank you for your reply :+1:. Yes I discovered that the hard way with this product. I reduced it down to half of what they are suggesting. I just need to gain a little more experience using it.

Do you have any suggestions on the Cal-Mag?

If you are using a decent soil, then you won’t need cal/mag until you get to flowering.


Ok, thank you for your help. Much appreciated :+1:

I am new here but I believe did experience a CalMag issue 2 weeks after sprout. Although I was using happy Frog I think if you are using RO water it might not hurt adding it. Here is a picture from an earlier post. Can somebody confirm this is CalMag deficiency please?

Mods, If this answer is wrong please delete to propagate misinformation.

Generally not necessary to add cal/mag until one nears flowering if in Fox Farm soils. One exception is if you are using high intensity lighting, which increases cal/mag demand.

It is indeed hard to hurt a plant with excess cal/mag, certainly far less probability than adding nitrogen, where we regularly see toxicity problems.

Imho people rely far too much on throwing cal/mag at problems assuming it will fix whatever issue is seen. I don’t see many issues that are truly cal/mag deficiencies. People get away with throwing cal/mag at plants precisely because it’s hard to hurt a plant with cal/mag. Others’ may disagree, but that is my opinion and I’ll stand by that opinion.

I grow in HF and have never needed to add cal/mag until flowering (8 - 12 weeks of veg.) I start adding it at 5ml per gallon (one gallon only) at the beginning of flowering with each watering. I’ve never had problems with it.


As I said I am not the expert but was just pointing a recent issue I had early in grow. Out of the 4 plants this one has been consistently having Issues but the other three were fine.

The issue also arose before I started measuring PH and TDS input/runoff as I thought I was safe with Happy Frog for a month. The most recent deficiency was probably lockout as Runoff was low. You have given input to some of my previous post so thanks for for your guidance