Hi im looking to change the substrate in my tank and was wondering whats the best way to go about it. I have pebbles at the moment that are holding far too much debris and crap. So i have decided to change to sand. As the tank is already set up with fish in it would it be ok to change the substrate. I thought about doing it in stages. First with taking the old substrate out and letting the excess dirt be filtered and monitor the water levels. Then once stable put sand in one end of the fish tank then the other not to disturb the fish too much. Any one else had any experience with changing?

Unless you want to take all your water and fish out before changing the substrates, you will have to do it with everything in place. I have changed substrates before without removing water or fish, it makes a complete mess of the water but if you do it gradually and carefully, it doesn't cause any problems. Just remember to turn your filters off when you are adding the sand, if you don't, they will probably suck quite a lot of sand up.

It may be easier if you remove some of the water. It'll be okay to turn everything off for an hour, your bacteria will not suffer too much.

Thanks for the advice.

When i put a UGF with a gravel tidy in my tank i did it all in one go. Firstly i did a 50% water change the day before i intended to change the substrate. The next day i changed the substrate. I removed all the decorations. I got a scoop and removed most of the gravel. Then i moved all the gravel left into one corner and syphoned it out. Your tank will get cloudy after doing all this, however this cloudyness soon goes.

When you add your new substrate makes sure it is cleaned and add it slowly to one end of the tank. When this piles up too high spread it around, and add some more. Then you just top up the water to the correct level. I then did another water change the next day. Test your water every day or 2 for a week just to make sure everything is ok with your water

Your fish will not be happy when you do this and may get a bit spooked at time and rush around the tank. Good luck