You are mentioning clown or citron gobies. Are you keeping SPS? They do better in tanks with branching type corals especially Acropora.
The clownfish are sort of a challenge in that they will be protective of their spawning area. Something to be aware of.
No reason to be upset with the Helfrichi. It is doing what it does. All fish are different and may not do what others report in a different environment.
Court Jester / Rainford's Goby is one possibility. Also captive bred. Tessellated Blenny is a nice option although reef structure, barnacle group if you have one. Starry Goby - also interesting.
You are working with 25 gallons of raw space not factoring in aquascape, equipment, and so forth so not a lot of options. Searching on "nano fish" will yield some decent results. May not find an open water but something like the Court Jester or Forktail may work. I wasn't going to reply due to the irritated comment because, again, fish are fish and do their own thing...
Hope your day is well.