Sorry to hear that, but I know exactly how it feels to have egg eaters. My prized Red Dragon pair just spawned and the male ate 99% of the eggs while I wasn't looking. So now I have only less then 10 babies to raise. Was so bummed because I've been fry-less for months. :(
From what I gather online, nobody knows for sure why or how to prevent that. There are a few possibilities (in order of likelihood):
1. The male was not adequately conditioned before the pair is introduced, causing the male to be 'tempted' by the more nutritious eggs. You can try stuffing him with more live foods more frequently maybe 1-2 weeks before spawning. And make sure his tummy is full before putting him in the spawning tank. Feed him in there if you must.
2. Most egg eaters tend to be virgin males with no experience with handling eggs. They should get their act together with a few more tries as they gain experience. However, if they still eat eggs by the 3rd or 4th time, then maybe he's just hopeless. Time to give up on him. If not, you're just going to have to hatch the eggs artificially.
3. He is frightened/feels threatened by movements around his spawning tank, which may cause him to give up on the spawn completely, eat up the eggs to conserve enough energy and nutrition to spawn another time. Try covering the spawning tank with newspapers to reduce distraction.
4. The whole batch eggs could be unfertilized and the dad is just doing his job cleaning up the mess. Though I think this is unlikely if the dad had been putting and rearranging the eggs on the nest diligently before eating them. It's more normal for him to eat 10%-20% of the eggs (unfertilized ones) rather than the whole batch.
I'm treating my case as a combination of no.1 and no.2. Fed him lots of frozen bloodworms a week now and since I can't use my red dragon female again at least for another week, I have to make do with a red cambodian CT female in my sorority tank from my previous spawn. Just to see if he still eats them. I'm not too confident he won't..but at least if he doesn't, I'll end up with maybe some red dragon CTPKs, hopefully.
Was the male kept alone? or in community tank?
It is his first try?
Sometimes when the eggs are not fertilized he knows this and will eat the eggs. If they were disturbed during spawning sometimes it does not go well. Are they isolated? or in a place with a lot of traffic?
If he is new to it, yes he will eat the eggs... Most of the time they do. I think I found it is the female I was breeding (who breeds very well with any male) since my doubletail ate the eggs twice, my CT ate the babies once and eggs again... Try different females, condition with more foods, do more water changes too... Find something that works for him :) Have him in a room where it is low traffic, and cover the tank sides with paper or something to give him security.
Not all egg/fry eaters are young males. Some mature males are also psycotic eaters. If that male’s genetics is important, the eggs can be hatched artificially. Basically good eggs will hatch if they’re not overcome by mold/fungus regardless of care. There are a number of ways of doing this – like breeding, there is no right nor wrong way.
If you want to give the male another chance, rest him for a month before spawning him again. IME constantly breeding egg eaters (interval of 1-2 weeks) will make them a psychotic egg eater. Spoil him will his favorite foods. If he still eats his eggs, then you have to artificially hatch the eggs.
I use an ice cream bowl; a 1ltr oval plastic bowl or a round plastic cereal bowl (about 15cm in diameter). Put in about 2cm of new, clean water, carefully spoon the eggs into the bowl. Spread them as best I can - to avoid bad eggs ruining good eggs. (btw, eggs that have been picked up by the parents will float - IDKW). Then place the lid on top to reduce bacterial growth (not secured - so it's easy to take off without disturbing the eggs).
I don't need heaters (I live in a tropical area). If temps are low and unstable I simply place it in a warm tank or place it my room. If you place it in a heated tank, make sure the bowl floats evenly (not tilt). Then I cover the whole tank to reduce debris getting into the bowl.
After 24-48 hours, they begin to hatch. I pick up the rotten eggs with a small stick like a tooth pick (you could use tweezers). Sometimes good eggs get caught in rotten eggs but will hatch so I don't immediately throw them away..... Then I slowly add 100% water to the previous water using a drip system ..... don't make the water drop. Make it "flow" from the side of the bowl. Hopefully this will reduce ammonia.
Sometimes I feed a drop of eggyolk once they’re free swimming. 1-2 days later, I acclimate them to a grow out tank. Then release. The percentage of hatch depends on how good the eggs were in the first place. I've had 0% hatch. But have also had 100% hatch. My average is around 60%.
If all that is too troublesome, you could leave everything in the breeding tank - use lower water level (about 3" or so - actually this has little affect except it makes me feel better. LOL). Take out both parents when they're done spawning and hope for the best. ..... Good eggs will hatch. And strong fry will survive. But you might not get that many with this method, specially if you have tons of snails in there.
So what if the male is in sight with guppy fry?Not in the tank but next to the tank.
When the male spawn,the female's anal is pointing away from the males.Does this mean the eggs were not fertilized?
Luckly i have another sibling male and 3 other females as back up.
Take the parents out. Parents are always trying to be so helpful. Just take them out and let the spawn live in peace. Take her out and as soon as Dad has blown a few more bubbles for the eggs, take him out too.