places – “My Family doesn’t use it for the seder since there is a shitta that says it is Shakol.”
Although you should respect your family minhag, that is not the ruling of other poskim.
Chazon Ish (Kilayim 13:16) conclusively proves from Gemara, Pesachim 35b that wheat that grew unattached to the ground (e.g. in a flowerpot) may be used for matzah at the Seder. Since many of the requirements for marror, including that it must be produce of the “land”, are derived from the halachos of matzah (see Gemara, Pesachim 39a) it follows that hydroponically-grown marror may surely be used at the Seder.