Probe holders and probes touching each other...

[Gordonious]

I like my set ups to be clean and neat, I don't like trusting suction cups, and I hate cords going everywhere. I've used a probe holder in the past and I really liked it. Two more companies just came out with probe holders as well recently. That being said in the New User guide it recommends the probes be kept 6" apart. Can’t happen in a 5” probe holder with 4 probes.

How significant of an issue is it having them close together?

[schwaggs]

Which controller do you have? With the Apex, this is usually a non issue since it has galvonically isolated probe circuits. I have my ORP, pH and Temp probes a probe holder about 1" apart and have not had any issues. I used the same probe holder for my ACIII without issues as well but YMMV. :)

[Gordonious]

Thanks, schwaggs. I have an Apex. It is always rough to make a decision when you are told what is ideal, but aren't really told the odds of having an issue if you ignore the ideal. I have a friend who I'm helping build a new sump for and I'm envisioning having an acrylic rim on the back of his sump with holes placed in it every 7" for probe holders designed to be put into reactors... not sure if I am going to go to that level or just use a standard off the shelf 4 probe holder. I think I will start with ordering myself a probe holder, so regardless I have experience with them being closer together and can see the negatives... but will I or are the negatives a slight variance in the readings vs a drop off of single.

So glad I'm not Neptune building these things. They are not a simple little toy by far.

Not familiar with YMMV, but guess this is similar to your results may vary?

[schwaggs]

YMMV - Your mileage may vary :)

I think the negative (if it occurs) is drifting pH or ORP readings. They jump around without any reason or pattern.