Hi, Nice looking plant :) I can see alot of open grow questions could you please remember to select a grower reply as an answer if they helped :) So yes you are correct EC meters are fully utilised by people doing hydroponic grows. This does not mean you cannot use one too. When you mix your feed and check your ph it is then advised to check your EC or PPM these readings are quite important. EC being electrical conductivity and PPM being part per million. Many growers especially in the UK will use the EC calculation as it relatively easier to understand compared to PPM. Now these reading are important to stop issues like this. If you grow in soil you have the perk of being able to test your run off. That is a huge advantage because you can actully work out how much feed or how little feed your plants are actully using so then you can see if they are not taking up a certain nute or they havent got enough or too much. EC levels are not Law and each grower uses different levels. Most mainly follow the feeding chart given with the brand of nutes they are using so this can give you a very good base on where to start and finish your feed for the whole life cycle of your plant these feeding tables are really easy to find online and they can help so much when it comes to giving your plant what she needs how the brand have already tested what works well with cannabis so if you replicate that you should not get any troubles. :) You can bet by without an EC meter though it is alot of luck. EC meters are reletivly cheap even the small pen ones will give you a round about guess at the current ec which is better than nothing because atleast then you could tell if she has too much or too little :) Good look for the rest of the cycle keep it green :) 👊