I wouldnt say you were overstocked but plecs are messy. Lots of people buy them thinking that they will clean up all the uneaten food but they actually cause a lot of waste themselves. Try vacuuming the bottom of the tank on a regular basis.This is one of the problems with a sand substrate as it shows up all the dirt if its a light coloured sand. Gravel in my opinion is a much better substrate for Oscars. Now only that idf there is debris on the bottom it will drop in between the gravel and can be dealt with by the beneficial bacteria on the gravel surface. The problem with sand is that you dont get a lot of good bacteria in it and it can become stagnant. your clown loaches will help to move the sand around as they root around for food in it but i think that gravel is a much better substrate than sand.

reguardless of what substrate you use your fish are going to produce the same amout of waste.if you find there is too much waste sitting on top of the sand try increasing the vacumming in your tank. if you change from sand to gravel the only difference will be in the amount you can see.your tank wont be cleaner it will only seem to be.

well last nite i decided after all to take the sand out and have it with no substrate, i dont look as good but it is alot easier to keep clean as after every feeding i just position the filter on the opposite side of my tank to push all the waste towards the intake tube, and wallah no more waste and debris
the only thing is a mate came round who used to keep oscars and he said that im well overstocked he said that my tank is only capable of 1 oscar is this true?????? i might get rid of the biggest convuct as he is bullying the littler one, then i could get rid of the biggest plec then that leaves my tank to 2 juvenile opscars, 2 clown loaches, 1 convict, 1 plec

is that better???????

well your tank is 270 l thats works out to about 65 imp gals. if your plan do not include upgrading your tank in the upcomming year i would rehome both the plecs, convicts, and one of your oscars. because the clown loaches grow so slowly they might be ok.
the general rule of thumb is one oscar per 55 imp gallons.(without mates)

as for the substrate i would put something back into the tank be it sand(my fav,which can work the same way as you have it set up without anything)or gravel.

imo if you want to keep all the fish you now have you woild have to upgrade to a 150 gal tank and then it would still depend on how big your plecos get.

You are not overstocked at the moment, maintaining good water quality wont be too much work. However when they all get big it will be loads of work to keep nitrates down, you may even need another external filter. Test weekly, ammonia and nitrite should be zero (if they are above and nothing has gone wrong then you will need another filter) If your nitrates go above 40 before doing a water change then you need to up the amount/frequency of water changes. When the water changes become too much for you, rehome some fish. The problem is that by then you might have become attached to them and not want to rehome some. I would get rid of a plec now as you only need one

well i finally decided to get rid of a convict but when i went to the tank to have a look for some reason the smallest con had vanished either it got ate by one of my oscars or it got sucked up my intake tube?????? i was gonna have a look in my filter but it would have done more harm than good wouldnt it???? so now im left with 2 oscars 2 clown loaches, 1 convict cichlid and 2 plecs
i might get rid of the biggest plec aswell because he makes more waste than he cleans up if you know wat i mean

well i was speaking to a mate and he sed that i was well overstocked which i dont believe one bit!!!!
what can i do to keep the nitrates down maybe if i do atleast 20% a week will that be enough to cope with the nitrates?????

any hints and tips regarding this matter will be appreciated