Mating Mayhem From Silver Tipped Tetras. Advice Needed.

I've got the same going on in mine with one of the male cherry barbs, Fiona... Frustrating as you say when everyone is nice and peaceful then one of them switches into football hooligan mode and starts bullying everyone else... 

Two suggestions: * catappa leaves can have a calming effect - although don't do what I inadvertently did when I added the cooled water that I'd boiled them in into the tank, resulting in an overdose;

Ahh I hve some, I'll chuck one in

* approach the tank as I do, giving a stern look and declaring that there will be no nonsense/bullying in the tank which at least can serve to distract them unless the behaviour is in full frenzied mode.

Believe it or not but I actually tried that, unfortunately I doubt they noticed as they whizzed past my finger in a mad blur. My son tried to film them before he went out but was gobsmacked firstly by the colour change and then by the speed. The males look nothing like the golden fish I've got now. They were a washed out yellow in the shop.

The rest of my fish apart from the cories are all kind of gathered in the middle of the tank and the stiphs are all hiding. My 'supposed rainbow' has a couple of shrimp in his pot with him

If it's anything like the way the tetras are, I have to move elsewhere to avoid feeling voyeuristic or seasick with that relentless and frenzied pursuit which lasts throughout the duration of the morning on those mornings when it occurs. Like your other fish, the harlequins just gather in the middle, looking perplexed or else go to investigate and "get sent packing".

I have a tank with CPDs which normally I rarely see. They spend all of their time hiding away in the plants, just nipping out for a second to grab food. However, starting yesterday and continuing this morning, they are racing around the tank like crazy, what looks like mating behaviour. Maybe the change of weather is having some sort of effect, we know that air pressure changes can bring about this behaviour. The Corydoras habrosus in the same tank are showing similar activity. The only other idea I have is that yesterday evening the sunlight was full on the front of the tank for about an hour, this rarely happens as it needs the sun to be shining at the right time of day for a few weeks each year, otherwise sunlight never reaches the tank. Allowing sunlight to fall on an otherwise dark tank is a commonly recommended method of inducing some fish to spawn so perhaps this is what is happening?? It was about this time last year that the CPDs spawned.

The sun was shining on the tank. I must remember to close the sitting room curtains when I leave in the morning, I forgot I did it last summer.

I have never yet seen a fish egg. The harlequins are perhaps still a bit young to be producing any but, in all the "shenanigans" of the tetras, I've never yet seen an egg / eggs produced. Granted, the two tetra females would have them devoured almost immediately but, considering the amount of time I spend with the fishtank in my line of vision, I would have thought I would have seen some. Perhaps the temperature isn't quite right.

What exactly do they look like - clear-coloured or not, size, etc?

You are unlikely to see eggs unless they are from cories, cichlids or similar which attach the eggs to a solid surface. Most fish scatter their eggs, which are very small and will be eaten immediately. Egg laying tends not to last long, maybe just a few minutes, often first thing in the morning. Once it's done, it could be weeks before those fish lay again. Harlequins are notorious for needing particular conditions and rarely breed in an aquarium.