We had a terrible outbreak of algae in the turtle tank. I removed the turtle and added bleach to the water to kill the algae. I then siphoned all but about an inch of the water out, put in clean water, and conditioned the water. I still smell bleach. I am unable to completely empty the tank of water. What do I need to do?
Bleach is extremely toxic to all aquatic life and even miniscule amounts of it - way below the concentration threshold needed for a human to smell its presence in water - could be harmful. Being able to actually smell its presence in water means that the danger level of its concentration is completely off charts and you definitely need to decontaminate the whole tank for the sake of safety of your turtle. I know that's what you explicitly said you are unable to do, but I honestly just don't see any other reasonable option in this case.
I assume that having conditioned the water means you've used aquarium water conditioner from pet store, meant to neutralize chlorine and chloramines present in tap water. As far as I know, aquarium water conditioners don't reliably neutralize bleach as they aren't made for this purpose - and even if they did, I wouldn't trust them to neutralize the amounts that are actually smellable.
If I were you at this point, I would completely empty the tank, thoroughly scrub its interior with a rough sponge to clean all algae and mineral deposits that could have potentially absorbed any residues of bleach, then flush the whole tank with an energetic and constant stream of tap water for at least 15 minutes. And that's just for decontaminating the tank - any substrate, decorations, etc. I would most probably just dispose of and get new ones - especially those things that I'd even remotely suspect of being porous. I would consider them all to be potentially contaminated and dangerous at this point.
If there is something in the tank that you absolutely and ultimately don't want to throw away, like an expensive piece of equipment - I'd attempt to flush it with an energetic stream of tap water, as reliably as I could, for a reasonably long time - let's say, for about 15 minutes.
For example, if there is a filter in your aquarium: I'd flush it with tap water, both on the inside and the outside; maybe also I'd fill some container with tap water and let the filter run there for some time, so it could flush itself on the inside. I'd also throw away all the filter media and replace them with brand-new ones.
Also, glass equipment - like thermometer and heater - shouldn't be impossible to decontaminate reliably, since glass is relatively inert and not porous. For these I'd go with the same scrubbing and flushing routine as for cleaning the tank.
I have to admit that I'm a bit obsessed with all the safety measures, but please realize how serious of a threat bleach is for the life of your turtle. I've read stories about people accidentally having fatally poisoned all the fish in the tank because they had used bleach to disinfect and clean some aquarium decorations, and the miniscule amount of bleach they absorbed apparently were enough to annihilate all of them. Of course, turtles aren't fish - it gives them a little "advantage" since, unlike turtles, fish use gills for respiration and thus their respiratory system is also the subject to damage from water-dissolved chemicals. But still, all the turtle's external mucous membranes are in contact with water and thus they are vulnerable to immediate damage, especially from highly corrosive and oxidizing chemicals as bleach.
I've also read stories about people using bleach in aquarium disinfecting and cleaning, but it's done extremely carefully to completely flush it off to not contaminate the water afterwards, and it's never actually added to the water with turtles or fish. I'd never advise using it nor use it myself - the harshest "chemical" I've ever used in aquarium cleaning was table salt, so my answer might be a little biased.
I was curious about this because at this very moment I have put bleach into the turtle aquarium and did it by adding a small measure of it, like a cap full, or quarter cup at most, while I had a hose siphoning out all the water. The turtles are safely out of the way in tubs.
The tank is 125 gallons, and no way will I empty it, ever, completely.
However, by siphoning down, and then refilling several inches at a time, the bleach level is dropping way down.
When I lived in a country where the wash water was contaminated with e. coli and worse, I learned how to batch chlorinate using a cap full of bleach to about 30 gallons.
Washed myself and all my dishes with this, and never got an infection. No more eye infections after that, no more diarrhea, and life was better. Used properly, bleach is your friend. But, you can't let your little charges drink bleach, either.
By the time I am done, not only is there no bleach smell at all, but after that is noticed, the water has been changed two more times.
Whatever concentration is left after that, is some ppm amount.
In an emergency, drinking water for human consumption is made using bleach. The recommendation is to NOT drink it if after two treatments there is still no smell of the bleach. For human consumption, a slight smell of bleach is considered necessary.
So, use your common sense. Do the research. Check out "water batch chlorination." And if you ask me, turtle skin is a lot tougher than human skin, in the water.
At least the aquatic turtles I think we are talking about here.
Let's keep Trump out of this, too.