What we had utilized here, to compare buffering to an ion exchange resin, was Amberlite CG-50. That variant is a relatively fine powder. There are likely other exchange resins that have similar properties that are not quite as fine but if your in-line filter has a fine enough mesh it would probably work fine.
Be aware that ion exchange resins can be tricky as they absorb and release ions to maintain a PH. And, what they absorb and release will vary depending on the resin type and how they are pre-conditioned (they typically should be conditioned first). For instance, some resins could absorb specific ions that you really don’t want it to absorb. Preconditioning can help such scenarios. Read the Nasa paper above to get a feel for some of the issues they had encountered while noting that it is an old paper utilizing only a single specific type of resin.
Here is the description for Amberlite CG-50:
General description
Amberlite CG50 is a weakly acidic, carboxylic acid type of cation exchange resin.
Application
Weakly acidic cation exchange resin useful for isolation and purification of cytochrome C, amines, drugs, metal ions, thrombin, and neutralization of solutions. Meets requirements of FDA Food Additive Regulation 21 CFR 173.25.
Amberlite CG50 has been used as a reference cation exchange resin for the examination of binding and elution of genotoxic aminopyridine impurities from pharmaceuticals on molecularly imprinted polymers (MIPs). It may be used for the purification of bovine lactoperoxidase prior to the investigation of inhibitory effect of propofol on lactoperoxidase.
Also, see the following regarding the Torus PHPerfect which uses ion exchange resins … but I do not know what type:
Also see:
Also, you may want to consider how this would work to your schedule. If you’re swapping the nutrient solution on a regular basis, you may not really need to overly buffer the solution. Or, you may want to consider formulating the nutrient solution to include a small amount of MES to slow any PH drift.
My opinion is to trial run your system to watch the PH behavior to understand the PH range, direction, and speed … then consider a buffering or ion exchange resin solution. If you feel this system is susceptible to infection, this probably can be evaluated prior to adding any plants into the system.