sand to gravel

Question
Hi Renee,

I asked a question earlier about helping me identify an arowana but I also have a question about transitioning from sand to gravel. I have a tiger oscar and a lemon oscar that are 7 inches and 6.5 inches respectively. They're in a 75 gallon setup and I have been using sand as a substrate. However, the oscars, Bartholomew & Leopold, are always digging and kicking up sand that then gets sucked into my canister filter. I wanted to find out if there is a certain way to remove the sand and add gravel without having to take out most of the water.

Thank you for your time and advice.

Answer
Hi Ryan,

Well, I haven't got to the other question yet.  It's next on the list if it's in my box. :)

So, let's start with 75 gallons and an Arowana.  Yikes.  This aquarium is going to be way too small for it as it grows and once it reaches a foot, you need to move it to a 250 gallon aquarium, because they gain in length incrementally from that point forward.  It will require 250 gallons, at least, in captivity.

The best way to remove sand, especially in a tank that has a canister filter, is to drain the tank and do so that way.  There are several reasons I advise this method.

1. Canister filters work on a biological filtratoin method.  Yes, they require cleaning bi-weekly to monthly (although pet stores ill advise to clean them every 3 to 6 months) and most owners do not do this.  So, the filters are basically full of nitrates which feed back into the tank.  If you can take your water out and put it into a white bowl and it's not completely crystal clear, then there is too much waste in the water from using the biological filter.  If you do this and it's clear, then there isn't an issue.  Most people with fresh fish don't test their water, so knowing the exact amount of nitrates/nitrites and ammonia is pretty rare when they write to me, but the bowl-method is a great way to see if there is a water clarity issue.  If not, kudos to your upkeep. :)  

2.  If you take the gravel out while the tank is full, anything in the gravel (ie: waste and poop) will be thrust into the water immediately.  That will immediately taint the water with waste, bringing quality down.

If you wish to remove sand while the tank is full, you can do so using a large capacity hose.  You can get lengths of hose at Home Depot and use those to siphon both water and sand out together, but it will again, drain the tank.

Alternatively you can take a gallon jug, cut the top off and leave the handle, making a scoop out of it.  Lifting sand inside the jug will be simple, but again, you will have a quality of water issue when done.

If you have ever seen ammonia poisoning, or nitrate poisoning, it's so sad.  The fish suffer greatly over a period of time and die a terrible death.  This is why I advise not doing it while the tank is full.  Once waste permeates into the tank, it will indeed cause an ammonia spike, and your fish will have to either live through that spike or may die from it.

I hope this answer helps. I've tried to give you a broad spectrum answer so you can consider both sides of the coin. :)

I will get to the next one in a moment...

Renee