Why are neons out of the question? Are those H&TLs bullies? This would be my primary reason not to try that combination, and then aesthetic considerations.
I agree with this. In addition to the impact of feeding, tetras have a much lower bioload than guppies. They produce only a tiny fraction of the waste that guppies produce.
] My H&Ts will chase each other around, but I've never seen any actual damage done, no actual nipping, more like bumping and "Let's swim real fast through these plants -- tag, you're it!" and "I'll get you for that!" but then in a few seconds the chaser forgets why he/she was chasing. I do have a plump female black neon who claims half the 6G tank and chases others away (they keep returning) -- until yesterday, when my smaller male BN turned the tables and was chasing her everywhere. Ah, sex! But I find H&Ts to be easy going.
Your reply to DebbyS was a bit harsh for someone only trying to offer her own experience...
Schooling fish like to be in groups around 5-7+ so you should be good. As for bioloading, I often find feeding is the largest factor in determining my maintenance routine. Although clearly the bio-mass in a tank plays a big role.
If your Sig reflects your 20G tank and you are adding another 5 H-n-TLs, you will quickly be quite full in there. Are you planning on moving the frys out? Also, the guppies will just keep having more and more babies!
If you have soft water, try it. In hard water, both species tend to look a bit dull, and rummynoses might not do well.
