CichlidFish.com - Fish That Think.

I have an albino (or it may me a very uncolorful red) and a tiger. they are about 1-2 years old. the white is 21 cm and the tiger is 23 cm. we also have a 38 cm pleco. the oscars have been doing the mating dance as described in this site and have cleared a place to lay the eggs, but have not yet layed any. how long before they will? we have a 55 gal tank. also is it rare or common for a tiger to have a fully formed circle on the tail fin.

Breeding depends on a lot of factors.
One thing to keep in mind, is if you have a pair. If you only have two Oscars, if they are a Female/Female, or Male/Male, they may do mating behaviour, right down to cleaining a spot in the tank. If its a Female/Female, they will lay eggs, if its a Male/Male, you don't get any eggs.
Another thing to keep in mind, plecos, have been known to eat the eggs, at night. So if they have laid eggs, it is possible the pleco ate them. Just some things to keep in mind.

thank you. we have read many of your posts on this site and they have been very helpful. we have not as yet seen any eggs so we may not have a pair. they have stopped doing the dance.

we seem to keep having a problem with our ph and our nittrates we have treated and have cleaned. do you have any suggestions?

I wouldn't worry too much about pH, since oscars can handle a pretty broad range, as long as it doesn't fluctuate much and it is not too acidic, ie under 6 or over 8.5
As far as nitrates, just increase your water changes and/or gph filtration etc...get biowheels or bio-balls, something for bacteria to live on etc if 'nitrites' are high.